JPH08336832A - Fiber-reinforced pellet structure for thermoforming - Google Patents

Abstract

Kind Code: A1 Abstract: The present invention provides a fiber-reinforced pellet structure for thermoforming, which has an increased fiber content and is excellent in wetting by an impregnated polymer of individual filaments. A continuous structure having a length of 3 to 100 mm, comprising a thermoplastic polymer and at least 30% by volume of parallel aligned reinforcing filaments and having a void content of less than 15% is fine. It is in the form of chopped pellets and is constructed so that the individual filaments are substantially wetted by the thermoplastic polymer in the melt pultrusion process.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fiber-reinforced pellet structure for thermoforming, and more particularly to a fiber-reinforced pellet structure for thermoforming containing a thermoplastic resin or polymer and a reinforcing filament.

[0002]

2. Description of the Related Art Conventional production of fiber-reinforced pellet structures is carried out, for example, by a solvent impregnation method, a melt impregnation method or the like. The melt impregnation method includes, for example, a melt drawing method. The melt pultrusion method, or abbreviated pultrusion method, can be carried out by passing a tow or roving of glass fibers through a bath of low viscosity thermosetting resin to impregnate the fibers. The structure thus obtained is subsequently cured by heating. Although such methods have been known for at least 10 years, they have not been used commercially to any extent in the manufacture of thermoplastic resin impregnated structures. The reason for this is that it is difficult to wet the fibers when drawn through a viscous molten resin. The resulting product has unacceptable properties as a result of poor wetting.

The efficiency of a particular method is that it wets the fiber and thereby provides the basis for maximizing the very high levels of physical properties inherent in continuous fibers, such as glass fibers. , Can be evaluated by measuring the extent to which a product having a flexural modulus that reaches the theoretically attainable flexural modulus is provided.

The theoretically achievable flexural modulus is calculated using the simple rule of mixtures as follows: E _L = V _f E _f + V _m E _m where E _L is the composition Is the vertical modulus,
V _f is the volume fraction of the fiber, E _f is the flexural modulus of the fiber, V _m is the volume fraction of the matrix polymer, and E _m is the flexural modulus of the matrix polymer. .

If a conventional high molecular weight thermoplastic resin melt is used for impregnation of continuous roving, a high level of flexural modulus cannot be obtained.
For example, US Pat. No. 3,993,726 impregnates continuous rovings in a crosshead extruder under high pressure, pulls the rovings through a die, and cools and shapes the rovings to produce void-free molded articles. An improved method of making is disclosed. The product obtained with polypropylene is shown in Example 1 and, for a glass fiber content of 73% by weight, only about 6 GN / m 2.
^{It has} a flexural modulus of ² , ie 20% of the theoretically attainable value. It would be desirable to be able to produce materials with flexural modulus levels approaching those theoretically attainable.

[0006]

DISCLOSURE OF THE INVENTION The object of the present invention is to realize the above-mentioned problems of the prior art.
Particularly in the fiber-reinforced pellet structure, the content of the fiber is high, the degree of wetting of individual filaments wetted by the resin melt is high, and it is possible to maintain the agglomerated state in the pellet structure. To provide an improved fiber-reinforced pellet structure in which the appearance of the molded product obtained when producing a molded product from the product is good and the filament length in the molded product is not lost. is there.

[0007]

According to the present invention, as a means for achieving the above-mentioned object, it has a length of 3 to 100 mm and is aligned with a thermoplastic resin in parallel with at least 30% by volume. And a pelletized structure having the following formula (I):
Void content defined by:

[0008]

[Equation 2]

Has the form of pellets chopped into a continuous structure with less than 15%, and the individual filaments contained in the pellet structure have the above-mentioned thermoplastic resin in a melt pultrusion process. That is substantially wetted by, and that the pellet structure has the form of individual filaments that are injection molded to randomly disperse the filaments in the resulting article after molding. And a fibrous reinforced pellet structure for thermoforming, characterized in that at least 50% by weight of the filaments can be shaped into a shaped article having a length of at least 3 mm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to its preferred embodiments. In the following description, in order to facilitate understanding of the present invention, the fiber-reinforced composition, the fiber-reinforced structure, which the present inventors also invented,
Then, the fiber-reinforced pellet structure of the present invention will be described in connection with the description of the fiber-reinforced molded article.

The present inventors have recently found out that
Materials having flexural modulus levels approaching theoretically attainable levels are those made by the continuous process and contain at least 30% by volume of the structure of reinforcing filaments extending in the machine direction of the structure, and ASTM D79
A thermoplastic resin or polymer and a reinforcing filament, characterized in that the flexural modulus of the structure measured according to 0-80 is at least 70%, preferably at least 80% of the theoretically attainable flexural modulus. It is a fiber-reinforced structure containing. Interlaminar shear strength of these structures, greater than 10 MN / m ^2, preferably greater than 20 mN / m ^2. The preferred thermoplastics for use in this invention are crystalline polymers having a melting point of at least 150 ° C and amorphous polymers having a glass transition point of at least 25 ° C. For optimum rigidity, the thermoplastic should have a flexural modulus of at least 1 GN / m ² , preferably at least 1.5 GN / m ² .

The fiber-reinforced structure described above has a continuous alignment.
The various methods by which the wetted fibers can be wetted well
Can be manufactured. In one of these methods, melt viscosity
Degree is 30 Ns / m²Smaller, preferably 1-10 Ns /
m²Through the melt of the thermoplastic resin, which is
Continue pulling filaments to melt them
It consists of wetting with resin, in which case the filament
Are arranged along the pulling direction
A method of making a fiber-reinforced composition is provided. As needed
The impregnated filaments to form a fiber-reinforced poly.
It may be a mar structure. The viscosity of the thermoplastic resin is shear
Changes with velocity and is almost constant at low shear rates
Decrease from the value. In the case of the present application, the viscosity at low shear rates
Refers to degree (usually called Newtonian viscosity).
This viscosity is obtained by using a die with a diameter of 1 mm and a length of 8 mm.
It is conveniently measured using a tube viscometer, and the melt viscosity is
10 ³-10^FourN / m²Measured at shear stresses in the range
Is done.

Surprisingly, there are such resins
Or polymers to achieve satisfactory physical properties
Considered to be usually suitable in the field of thermoplastics
There is also the fact that its molecular weight is lower than
Regardless, the toughened composition has extremely good physical properties.
It has a physical property. Therefore, enhanced thermosetting
Manufacture resin or polymer composition by pultrusion method
The viscosity of the thermosetting prepolymer in the impregnation bath is
Typically 1 Ns / m for good wetting of the fibers ²Less than
Is. The reason why this low viscosity value can be used is because
The mer may then be converted to a solid form by thermosetting.
And there. In contrast, thermoplastics or
Limers are usually fully polymerized solid materials and
By heating and melting the thermoplastic polymer
It is obtained in liquid form. However, acceptable
A conventional high molecular weight resin with physical properties
The melt viscosity of the polymer or polymer is usually 100 Ns / m²To
Exceed. Pultrusion using a melt of this high viscosity
By law it is not possible to obtain proper wetting of the fibers. Melting
By raising the melt temperature, the melt viscosity can be lowered to some extent.
But below the decomposition temperature of the thermoplastic resin
The possible decrease in viscosity at temperature is usually inadequate
It

Low enough to give a sufficiently low melt viscosity
Using a thermoplastic resin with a high molecular weight, a pultrusion method
Properly wetting the fibers at
A strong product is obtained. Therefore, the melt viscosity is 30Ns
/ M²Smaller, preferably 1-10 Ns / m ²Between
Through a melt of a thermoplastic or polymer,
Draw multiple continuous filaments to create a filament
Wetted with molten resin.
These filaments are aligned along the pulling direction
Fiber reinforced thermoplastic compositions are also provided, characterized in that
Is done. The manufactured fiber-reinforced structure is less than 15%,
It should preferably have a void content of less than 5%.

The term "continuous fiber" or "plurality of continuous filaments" is sufficient to pull through a molten resin or polymer under the processing conditions employed without breakage at a frequency that renders the treatment infeasible. By any fiber product, such that the fibers have sufficient length to form rovings or tows of sufficient strength. Suitable materials are glass fibers, carbon fibers, jute and high modulus synthetic polymer fibers. In the latter case, it is important that the polymer fibers satisfy the condition that they are strong enough to be able to be pulled through the resin melt without causing disruption to the process. In order to have sufficient strength to be pulled through the impregnating system without breaking, the majority of the continuous fibers of the fiber product are oriented in one direction, and the fiber product has a majority of the continuous fibers. Align and pull through the molten resin. Textiles such as mats composed of randomly arranged continuous fibers are not suitable for use in the present invention unless they form part of a fiber structure in which at least 50% by volume of the fibers are aligned in the pulling direction. Appropriate.

The continuous fibers can be in any form with sufficient integrity to be drawn through the molten resin, but conveniently all of the fibers are aligned along the length of the bundle. A bundle of individual fibers or filaments (hereinafter referred to as "roving"). Any number of such rovings can be used. In the case of commercially available glass rovings, each roving can consist of up to 8000 or more continuous glass filaments. 600
Carbon fiber tapes containing zero or more carbon fibers may be used. Fabrics woven from rovings are also suitable for use in the present invention. The continuous filaments may be treated with any conventional surface sizing, especially those designed to maximize the bond between the fibers and the matrix polymer.

In order to achieve the high level of flexural modulus enabled by the use of the present invention, it is necessary that as much of the surface of the continuous filament as possible be wetted with molten resin. Thus, where a fiber is composed of multiple filaments, the surface of the individual filaments that make up the fiber must be wetted for optimal effect. Where the filament has been treated with a surface sizing or fixing agent, the resin will not come into direct contact with the surface of the fiber or filament due to the interposition of the sizing agent. However, as long as good adhesion is achieved between the fiber and the size and between the size and the resin, the products of the invention have a high flexural modulus and the size is generally obtained. Will enhance the nature.

The thermoplastic resin or polymer used in the above method has a melt of less than 30 Ns / m ² ,
It may be any polymer that melts to form a cohesive mass, preferably so long as it has a viscosity of less than 10 Ns / m ² . In order to achieve acceptable physical properties in the reinforcing composition, the melt viscosity is preferably above 1 Ns / m ² . As indicated above, the choice of polymer in the required melt viscosity range depends primarily on the molecular weight of the polymer. Examples of suitable polymers are thermoplastic polyesters, polyamides, polysulfones, polyoxymethylenes,
Polypropylene, polyarylene sulfides, polyphenylene oxide / polystyrene blends, polyether ether ketones and polyether ketones. Various other thermoplastic polymers can be used in the method of the present invention, but polymers such as polyethylene will not provide such high strength compositions.

In the method of impregnating the fibers of the roving, in addition to using a resin or polymer of suitable melt viscosity to cause proper wetting, it is possible to maximize the penetration of the melt into the roving. is necessary. This involves constructing the rovings into individual constituent fibers, for example by imparting an electrostatic charge to the rovings before they enter the molten resin, or, preferably, by spreading the rovings while the rovings are present in the molten resin. Separation into filaments can be done by separating as much as possible. This is conveniently accomplished by passing the roving under tension over at least one, and preferably several, spreader surfaces. Fibers that have been opened and resin impregnated, for example, by consolidating the opened fibers by drawing impregnated rovings from the melt through a die,
With the addition of more work, a further improvement in wetting is obtained. The die can have the desired profile for impregnating roving, or the impregnating roving can be passed through an additional sizing die while the resin is still flowable. Surprisingly, it would be advantageous if the die were cooled to achieve satisfactory sizing and smooth passage through the die. When the impregnating roving is discharged from the bath in the form of a flat sheet, additional work can be added by passing the sheet between a pair of rollers.

The speed at which the roving can be pulled through the impregnation bath depends on the requirement that the individual fibers be properly wetted. This will depend, to a large extent, on the length of the passage through the bath of molten resin, and in particular on the degree of mechanical expansion effect that the rovings will undergo in the bath. The speeds achievable with the method of the present invention are at least comparable to those achievable with the pultrusion process of thermosetting materials. This is because the pultrusion process is limited by the time it takes to complete the necessary chemical reaction after the impregnation step.

In one preferred embodiment, the spreader surface over which the roving is drawn to open the roving heats the spreader surface to a temperature above the melting point of the particular resin or polymer to be used for impregnating the roving. Equipped with an external heat input section for. By this means, the melt viscosity of the resin in the localized areas of the spreader surface can be maintained at a value much lower than that of the resin in the majority of the impregnation bath. The advantage of this method is that it heats a very small portion of the resin to a relatively high temperature, thereby minimizing the risk of the major portion of the resin in the bath breaking down,
The reason is that a low impregnation viscosity can be obtained. This results from the fact that the resin supply to the bath is continuously replenished, so that it is possible for some resin to remain in the bath for a period of almost unlimited duration during a given treatment period. The problem to do is greatly reduced. Therefore, some of the resin present at the beginning of the treatment period may still be present in the bath at the end of the treatment period. Despite this long residence time in the bath, such resins will experience a less severe thermal history than if the entire resin in the bath were exposed to high temperatures to obtain a low viscosity throughout the bath. Let's do it.

A further advantage of the local heating method is that a resin or polymer having poor thermal stability can be used. In addition, the lower degradation resulting from the lower total thermal history allows higher temperatures to be locally used due to the formation of lower viscosity melts, allowing higher molecular weight resins to be used.
The supply of resin to the impregnation bath can be in the form of a resin powder that is melted in the bath by an external heating element or by a heated spreader surface located inside,
Alternatively, the molten resin can alternatively be fed to the bath using, for example, a conventional screw extruder. If the bath has a heated spreader surface, the resin melt delivered from the extruder should be at the lowest temperature possible to minimize thermal decomposition. The use of melt feeds is easy to start, has good temperature control, and, especially when producing very thin structures, the formation of lumps of unmelted resin which causes various processing problems. It has the advantage of being avoided.

The impregnated fiber product can be drawn through a means for consolidating the product, such as a sizing die. The temperature of this die has been found to have a significant effect on this method. It is expected that a thermal die should be used to minimize friction in the die and promote consolidation, but it was found that the temperature was maintained above the melting point of the resin used. The die causes extraordinary sticky slip behavior as the product is drawn through the die. It has been found preferable to use a cooled die and to ensure that the surface temperature of the pultruded portion entering the die is no more than 20 ° C. above the softening temperature of the resin. "Softening temperature" means the lowest temperature at which a resin or polymer can be sintered. This can be accomplished by blowing air over the race in the passage between the impregnation bath and the die and / or by spacing the die from the impregnation bath.
If the pultruded part is overheated, the resin will be squeezed out as the product enters the die. This leaves deposits at the entrance to the die, which deposits accumulate and
As the pultruded portion passes through the die, it may be scored. The pultruded part should not be cooled below the softening point of the resin. Because it is too difficult to shape the product with a sizing die.

The dimensions of the fiber reinforced product can be varied as required. Thin sheets can be made by separating the fibers of rovings by passing a number of rovings over a spreader surface so that the fibers form a band in abutting relationship. When the die is used to tie the fibers together, the structure will take the form of a sizing die cross section. This allows any required thickness, eg 0.2
Articles with a thickness or linear profile of 5 mm to 50 mm can be formed. 0.05 mm when the means for consolidation comprises a nip formed from at least one pair of rotating rollers
Alternatively, a sheet having a thickness less than that can be manufactured.

In a further method of producing fiber-reinforced structures, it has been found that satisfactory wetting can be achieved even when the thermoplastic resin used has a melt viscosity of significantly more than 30 Ns / m ² . Thus, tension is applied to and aligned with a plurality of continuous filaments to form a band of adjacent filaments, such that a nip is formed on the heated spreader surface between the band and the spreader surface. And feeding a thermoplastic or polymer feed at the nip, where the temperature of the spreader surface is
Provided is a method for making a fiber reinforced composition such that when the continuous filament is drawn thereon, it is high enough to form a resin melt of a viscosity that allows the continuous filament to be wetted. The resin melt at the tip of the nip preferably has a viscosity of less than 30 Ns / m ^2, but the high back tension on the filaments to be fed to the spreader surface ensures that resin impregnation in the nip region is suitable. As a result, it is possible to produce impregnated bands at viscosities significantly higher than 30 Ns / m ² . Thus, this method provides a means of maximizing the molecular weight of the resin that can be used in the thermoplastics extrusion process.

In one embodiment of this method, continuous filaments are most suitably tensioned and aligned by pulling them from a roll or reel onto a series of spreader surfaces, such as the surface of a rod. It This allows the bundle of filaments to be spread as far as possible into the individual filaments under considerable tension. These filaments are guided to form bands of adjacent filaments as they pass over the heated spreader surface. The shape of the spreader surface and the contact angle between the filament band and the spreader surface should be such that a nip is formed between the band and the heated spreader surface. The thermoplastic powder is fed to the nip and the heated spreader surface is maintained at a temperature sufficient to melt the thermoplastic. As the band passes over the heated spreader surface, the melt impregnates the fibers of the band,
Get wet.

The method further comprises providing at least one additional heated spreader surface to form a second nip with the band of at least partially resin impregnated fibers with the spreader surface. This nip can be modified by allowing an additional feed of resin to be impregnated into the band of fibers. The surface of either of the partially impregnated bands can also be used to form the working surface of the nip.

The amount of resin or polymer in the reinforced structure is largely controlled by the tension exerted on the band and the length of the channels through which the band contacts the heated spreader surface. Thus, when the band is under high tension and is in substantial surface contact with the spreader surface such that the band is pressed hard against the spreader surface, the resin content of the reinforced structure is low tension / short. Will be less than under the conditions of the contact passage.

The heated spreader surface and any subsequent heated or cooled surface used to improve impregnation or improve surface finish are preferably in the form of cylindrical bars or rollers. For example, the first impregnated surface can be a freely rotating roller, which is rotated by the band at the speed of the band so that the abrasion of the fiber prior to impregnation or sizing by the melt is minimized. Could be reduced to. It has been observed that loose fiber build-up on the band takes place through this system when the first roll rotates (freely or driven) in the direction of fiber movement up to the fiber speed. This self-cleaning action is particularly effective in preventing the accumulation of fibers on the first roll which can divide the band.
After the band has taken up some of the molten resin, preferably after additional molten resin is provided on the other side of the band by a second freely rotatable heated surface, the fibers are
It has a very low tendency to undergo abrasion and can be subjected to treatments to improve the wetting of the fibers. Thus, the resin-containing band can be passed over at least one roller driven in a direction opposite to the direction of movement of the band to increase local work input to the band and maximize wetting. In general, the degree of wetting and the speed of the method can be increased by increasing the number of surfaces on which work input is present.

Another advantage that the method of forming a nip using a band of fibers can offer the advantage of reducing the risk of disintegration (collapse) over methods that require the use of a bath of molten resin or polymer. To do. Therefore,
Due to the relatively small amount of resin or polymer present in the nip between the fiber band and the spreader surface,
It is not necessary to keep a large amount of resin at a high temperature for a long time. A scraper blade can be placed at the location where the polymer is fed to the nip to remove excess polymer that may accumulate and undergo thermal decomposition during processing.

When the product of the above process is required as a thin reinforced sheet, the product produced by impregnation in the nip is further passed by passing over or between additional heated or cooled rollers. It can be treated to improve impregnation or improve the surface finish of the sheet. Thin sheets tend to curl when one side contains more resin or polymer than the other. This can be avoided by placing an adjustable heated scraper close to the last roller in the roller system to remove excess resin on the surface of the sheet. The scraper bar should be at a temperature just above the melting point of the resin. For example, in the case of polyetheretherketone, which reaches a temperature of about 380 ° C. in the impregnation zone, the temperature of the scraper bar should be about 350 ° C.

The impregnated band can then be further processed depending on the intended shape and purpose of the final product. The open filaments in the impregnated band can be drawn together, for example, through a die to give a profile with a thickness that is significantly greater than the impregnated band. A limited amount of molding can be performed on such a die to obtain a molded profile.

The impregnated product of the above-described process is made into a long piece for subsequent use in molding processes requiring continuous products, for rolling or subsequent molding. You can shred. The continuous strip can be used to make an article, for example, by wrapping the heat softened product around a former, or by weaving a mat from, for example, a tape or strip of the product. The impregnated product can be chopped into pellets or granules in which the aligned fibers have a length of 3 mm to 100 mm. These things are
It can be used in conventional molding or extrusion methods.

When using glass fibers, the fiber content of the product of the invention is at least 50% by weight of the product in order to maximize the physical properties of the product. The upper fiber content limit is determined by the amount of resin or polymer required to wet the individual fibers of the roving. In general,
Although it is difficult to achieve good wetting with less than 20 wt% resin, good results have been the incorporation of 30 wt% polymer into a fiber reinforced composition using the method of the present invention. Can be obtained by

The product of the invention, formed by the method of impregnating adjacent bands of roving in the nip formed by the band and the heated spreader surface, comprises:
Usually, the impregnation system will be pulled as a band or sheet of material. This provides an intermediate useful for many applications. A thin band or sheet, ie 0.
Thicknesses less than 5 mm and greater than 0.05 mm are particularly useful and versatile.

The tape is woven using a tabby or satin weave, which terms are used in the field of textiles and are described in the "Weaving" section of the Encyclopedia Britannica. It is particularly useful in forming a finished article. The satin weave gives a particularly good product, as shown in the examples herein. Fabrics with very high performance are obtained with tapes produced according to the invention and having a width of at least 10 times the thickness. One important application is as a thin reinforced sheet, which consists of a ply of multiple reinforced sheets,
Can be used to form a reinforced article,
The reinforcement of each layer is then placed in the plane of the layer in the selected direction and the layers are compressed at a temperature sufficient to fuse the resin of the layers. The layer can be used as a flat sheet that can be molded in a mold during or after the fusing step, or else wrapped or molded on a shaping mandrel and having the shape of the mandrel after the fusing step. An article can be obtained.

Producing a reinforced molded article by, for example, wrapping a reinforcing filament on a forming mandrel and sandwiching a layer of polymeric film between layers of filaments and subsequently fusing the polymeric film is known, for example. , As disclosed in British Patent No. 1,485,586. The present invention is superior to such methods. The main advantages are that the use of high-cost preformed polymer films can be avoided, the content of the polymer can be controlled by the tension of the band, thus avoiding the provision of films of various thicknesses, and Advantages derived from the continuous nature of the method of the invention.

The pultruded article of the present invention is also suitable for being chopped to an appropriate size to selectively reinforce the article molded from a polymeric material. At least one preformed element comprising a product according to the invention is placed in a mold to strengthen selected portions of the finished molding, and a polymeric material is molded around the in situ reinforcement to create a shaped article. To form.

The present invention not only allows the fiber reinforcement to be placed in a molded article to obtain the maximum effect on the stress the molded article is subjected to during use, but also to provide such high strength articles. It overcomes the processing problems encountered when manufacturing differently. In particular, this method has a melt viscosity of 1
It can be used to produce such reinforced articles by the high productivity injection molding process using common thermoplastics or polymers of 00 Ns / m ² or higher.

In some applications, the preformed element may be
It is advantageous to use it at a temperature at which it is flexible so that it can be more easily placed in the mould, for example by wrapping a heat-softened preformed element around the mold insert. Will. The molding method used may be any method of forming a molded article in a mold from a resin or polymer material. The resin material may be a thermoplastic material that is introduced into the mold as a melt, as in the injection molding process, or as a powder, as in the compression molding process. The term "compression molding" includes the method of compressing resin powder without melting and subsequently sintering the "green" molded article out of the mold. The thermoplastic material that is molded in the mold is one or more monomers or moieties that are retained in the mold until they are completely polymerized, for example under the action of heat or a chemical activator or initiator. It can also be induced by introducing a chemically polymerized medium.

The resin molded around the preformed insert is preferably the same as, or at least compatible with, the resin used to impregnate the preformed insert. The impregnated product obtained by the above method comprises at least 3 mm of reinforcing fibers,
Special utility can be brought about when chopping into pellets or granules, preferably having a length of at least 10 mm. These products can be used in conventional molding processes such as injection molding and are superior to prior art products in the form of pellets. This is because the length of the fibers in the pellets is kept to a much greater extent than when using the prior art products. This greater fiber length retention is believed to be the result of greater protection imparted to the individual reinforcing filaments in the product of the invention, due to the excellent wetting by the resin resulting from the use of the aforementioned method. To be

This aspect of the invention is of particular importance. This is because it allows reinforced articles to be formed in flexible operations such as injection moulding, which uses a screw extrusion process to melt and homogenize the feedstock, and the fiber length is surprising. This is because it is retained at a high level and eventually physical properties are improved. The product of the invention thus makes it possible to obtain moldings from a molding process using screw extrusion, which moldings contain at least 50% by weight, preferably at least 70% by weight, of fibers having a length of at least 3 mm. To do. This is significantly longer than what would normally be obtained from commercially available fortified products. Another method for forming shaped articles by melting and homogenizing short length, ie 2-100 mm, reinforcement products of the invention is by calendering. For example, sheet products can be manufactured in this way.

The products of the invention suitable for injection molding can be used directly or blended with pellets of other thermoplastic products. These other products can be the same resin or polymer but with a higher molecular weight, or they can be different resins, as long as the presence of different resins does not adversely affect the overall balance of composition properties. it can. Other products may be unfilled resins, or may contain particulate or fibrous fillers. Blends with conventionally produced reinforcing molding powders, i.e. materials containing molding powders containing reinforcing fibers up to about 0.25 mm in length, are particularly suitable. This is because short reinforcing fibers do not contribute as effectively as the long fibers provided by the product of the present invention, but can maintain a high content of reinforcing fibers throughout the blend.

The shredded shape of continuous pultruded articles is also very useful as a feedstock for the process described in co-pending British Patent Application No. 8101822.
In the method of this British patent application, the fiber reinforced molded article is
A composition comprising a curable fluid as a carrier for fibers of at least 5 mm length is passed through a die so that as the extrudate leaves the die it relaxes the fibers and causes the extrudate to expand, leaving Produced by forming a regularly dispersed open fiber structure and compressing the manufactured porous structure into a molded article while the carrier is in a fluidized state.

The term "curable" means that the fluid "solidifies" in a form such that it retains the fibers in the irregular orientation that occurs during extrusion. Thus, for example, the curable fluid is extruded in the molten state,
It can be a molten thermoplastic material that then solidifies by cooling until it freezes. Preferably, the expanded extrudate is extruded directly into the mold chamber which has a means of compressing the porous extrudate into a molded article,
Then, the extrudate is compressed or processed into a molded article before or after the extrudate is solidified.

Since the extrudates formed in this way contain irregularly dispersed fibers, only the orientation of the fibers in the molding is the result of the compression process. This method can be used with high fiber loadings, ie, greater than 30% by volume. Since fiber breakage rarely occurs, molded articles with extremely high strength can be obtained, measured in all directions of the product.

At least 5 m of pultrusion product of the invention
Pellets obtained by chopping to a length of m, preferably at least 10 mm, are advantageous. The upper limit of length is determined by the degree of problems encountered in the material feeding the extruder that melts the product. At least 50
Lengths up to mm can be used, but the advantage of large fiber lengths is partly compromised, as their length increases the amount of fibers that break.

[0048] In order to achieve adequate wetting of the rovings, relatively low molecular weight resin or polymer, for example, below the 30 Ns / m ^2, preferably be a resin melt viscosity of less than 10 ns / m ² While it is surprising and surprising that such products have such high levels of physical properties, the present invention provides for increasing the molecular weight of resins in compositions by known methods. Does not preclude subsequent processing steps. Such techniques include solid state polymerization in the case of condensation polymers, the use of cross-linking agents or irradiation techniques. When cross-linking agents are used to increase the molecular weight, it is necessary to mix them homogeneously in the composition. This can only be done if they are already present during impregnation,
In such cases, care must be taken to ensure that the crosslinker is not activated prior to the completion of the wetting step.

[0049]

The present invention will be described in more detail below with reference to typical examples. It should be understood that the present invention is not limited to these examples. Example 1 Using a copolymer of polyethylene terephthalate in which 20% by weight of terephthalic acid has been replaced by isophthalic acid and having the intrinsic viscosity values listed in Table 1 below, in a bath at a temperature of approximately 290 ° C. A polymer melt was prepared. A roving of a glass containing 16000 individual filaments was drawn through the molten polymer over one spreader placed in the bath at a rate of 30 cm / min giving a residence time in the bath of 30 seconds. It was The impregnated rovings were drawn through a 3 mm diameter die in the bath wall and then cooled.

The melt viscosity and the intrinsic viscosity of the polymer in the polymer feedstock and in the fortified composition were measured. The wettability and void content of the fibers were evaluated by comparing the weight of the fully wetted length of the impregnated product with the same length of product of unknown wettability. The completely wet control material was obtained by pultrusion of a low viscosity melt at a very slow rate so that a completely transparent product was obtained. Thus, the completely wet standard was taken to be the sample that was made under conditions that were transparent and optimized the parameters suitable for wetting. Table 1 below
The value of the degree of wetting described in is derived from the following relational expression:

[0051]

(Equation 3)

Here, M ₀ , M ₁ and M ₂ are the same as defined above. The void content (%)
Can be obtained by subtracting the value of the degree of wetting from 100%, as indicated above. Product strength was evaluated by measuring the force required to bend and break a sample of 3 mm rods placed across a 64 mm span. The results obtained are listed in Table 1 below.

[0053]

[Table 1]

Example 2 The polymer used in Example 1 and having an intrinsic viscosity of 0.45 dl / g was evaluated over a range of melt temperatures and draw through rates. The results obtained are shown in Table 2 below.
Described in.

[0055]

[Table 2]

Example 3 PET having a melt viscosity of 6 Ns / m ² at 280 ° C.
The homopolymer was prepared as described in Example 1 with a diameter of 17
280 glass fiber composed of μm filaments
Used at 0 ° C., pultruded using a single spreader rod and a linear velocity of 30 cm / min to give a pultruded rod of approximately 3 mm diameter. The glass content of the product was changed by changing the number of strands in the roving fed to the bath. Flexural modulus and force at break were determined as a function of glass content using a 64 mm span. The results obtained are listed in Table 3 below.

[0057]

[Table 3]

These results show that the range is 50-65% by weight.
It is shown that the elastic modulus and the strength have an approximate plateau at the glass content of. Example 4 Conventional grade polypropylene has a viscosity above 100 Ns / m ² at lower shear rates and is not suitably processed by pultrusion. For example, the melt viscosity of "Propathene" HF11, a polypropylene homopolymer, is about 3000 Ns / m ² at 280 ° C. at low shear rates, and 2
It is about 10,000 Ns / m ² at 30 ° C. In order to prepare polymers suitable for pultrusion, "Propathen"
e "HF11 with 0.1% calcium stearate,
0.1% "Irganox" 1010 and 0.5%
"Luperco" 101XL ("Luperco"
101XL was an organic peroxide dispersed with calcium carbonate) to allow decomposition to occur. This formulation is 2 at 30 cm / min using a single spreader.
Pultruded at temperatures of 30 ° C and 290 ° C. Two
Wetting was poor at 30 ° C. (melt viscosity 30 Ns / m ² ). At 290 ° C (melt viscosity 17 Ns / m ² ),
Wetting was moderate.

Example 5 A sample of "Victrex" polyether sulfone having a relative viscosity of 0.3 was pultruded with the glass fibers used in Example 3 at 405 ° C and 21 cm / min using a single spreader bar. (Melt viscosity of 30 Ns / m ² ) reasonably wet drawn product was obtained. At lower temperatures, the samples were poorly wet when the viscosity was high.

Example 6 Wetting of rovings was clearly affected by the number of spreader bars, and under the same working conditions, increasing the number of spreaders achieved an increase in linear velocity for any degree of wetting. it can. The glass fiber used in Example 3 was pultruded at 280 ° C. using PET homopolymer using a single spreader and a speed of 20 cm / min to give a completely wet product (clear). The residence time in the bath under these conditions was about 30 seconds. With three spreaders, the linear velocity could be increased to 120 cm / min and a clear, well-wet pultrusion could be obtained.
The residence time under these conditions was about 10 seconds.

Example 7 Several polymers were used according to the general procedure of Example 1 to make pultruded parts from glass rovings containing 16000 filaments. Pass roving through molten polymer over one spreader bar 15
Subtraction at a rate of cm / min gave in each case a product containing about 65% by weight of glass. The polymers used, the melting temperatures used, the melt viscosities at those temperatures and the properties obtained are detailed in Table 4 below.

[0062]

[Table 4]

In the case of polyethylene terephthalate, the pulling speed was increased above about 15 cm / min and the effect of void content on physical properties was investigated. Table 5 below records the measured properties of the 3 mm diameter rods produced. As these data show, a void content of less than about 5% gives excellent properties.

[0064]

[Table 5]

Example 8 A sample of carbon fiber reinforced polyetherketone was
A carbon fiber tape containing 000 individual filaments was passed through a bath of molten polyetherketone to 40
It was prepared by drawing at a temperature of 0 ° C. and a speed of 25 cm / min. Flexural modulus of 80 GM / M ² , 1200 MN / m
The product was obtained having a ^second breaking stress and 70 mN / m ² of interlaminar shear stress.

Example 9 This example is to demonstrate how the mechanical properties of pultruded moldings vary with fiber volume fraction and resin type. The samples were compared at a fixed volume concentration. The low flexural strength of polypropylene-based composites reflects the tendency of the less rigid resin to fracture in the compression mode. Polypropylene resin is about 1 GN / m
Has a ^second modulus (modulus of elasticity), polyethylene terephthalate has a modulus of about 2GN / m ^2. Pultruded articles were prepared according to the general procedure of Example 1 with a preferred viscosity level of about 3 Ns / m ² of resin.

[0067]

[Table 6]

As this example shows, high modulus resins are clearly superior for applications requiring high compressive strength. Example 10 A sample of 64 wt% glass in PET was pultruded to
A tape having a width of 6 mm and a thickness of 1.4 mm was prepared. The tape was remelted, wound under tension on a 45 mm diameter former, solidified on the former and then allowed to cool. After cooling, the former was pulled out to obtain a tube of wound filament.
Tubes of varying thickness up to 4 mm were wound and formed in this manner.

Example 11 A 3 mm diameter uniaxially oriented pultruded sample based on PET containing 64% by weight glass was remelted and twisted into a helical shape. These twisted rods were bend tested and the stiffness breaking force and total work to failure measured. The total work of failure was determined as the area under the force-deformation curve to failure and, for convenience, is expressed here as a function of the area under the untwisted control sample.

[0070]

[Table 7]

As can be seen from the above results, 11 °
At, there is only a 10% reduction in stiffness and breaking force, while the total work to failure is increased by 30%, improving the balance of properties. At 23 ° both stiffness and strength are reduced by about 60% and the work of failure is 6
It only increases by 0%. Therefore, the optimum twisting is 1
It is shown to be about 1 °.

A pultruded article of a thermoplastic material is more suitable than a thermoset pultruded article because it allows the post-molding to be carried out easily and thus offers the advantage of this energy absorbing mechanism. Example 12 3 mm diameter containing 50% by volume of glass fibers in PET
Pultruded melts were melted at 280 ° C and then braided together. The braided product was less stiff than the uniaxially aligned material, but absorbed more energy in the impact failure test.

Example 13 A flat tape approximately 1.4 mm thick and 6 mm wide formed from a material containing 50% by volume (64% by weight) glass fiber in PET was released into an open tabby weave. Weaved together. Stacking 4 layers of the resulting fabric together, 28
A sheet having a thickness of 3 mm was manufactured by compression molding at 0 ° C. This sheet had the following properties: * Slightly lower values would be expected at an angle of 45 ° to the natural orientation of the fabric.

Example 14 Samples of various pultruded moldings were placed in conventional injection molding molds and compatible polymers were molded around them. The moldings had increased stiffness and strength. Thermoplastic pultruded moldings are particularly suitable for the purpose of strengthening the moldings in this way, since they can be produced with polymers which are completely compatible with the polymer to be molded around the reinforcement.

Example 15 A conventionally compounded material containing 65% by weight glass fiber in PET, chopped to a length of 1 cm, and containing 30% by weight short glass fiber in PET. And then 50/5
Diluted on a 0 basis. The mixture was injection molded using standard techniques to make ASTM bars and properties were compared to a conventionally compounded material containing 50% by weight glass fiber in PET.

[0076]

[Table 8]

Inspection of the ashed portion of the moldings revealed that the majority of long fibers were retained throughout the molding operation. It is believed that this unexpected property results from the low void content in the shredded pultrusion material or the high degree of wetting of the fibers by the polymer. Example 16 Various pultruded samples containing 60% by weight glass fiber containing PET and 60% by weight carbon fiber containing PEEK were cut into 1 cm lengths and described in British Patent Application No. 8101822. Molded according to the method described above. In the method of this UK application, the expanded reinforcing material is produced by extrusion through a short length, preferably zero length die, followed by compression molding to give a three dimensional product containing 60% by weight of long fibers. A molded product was produced.

The pultruded material is particularly suitable for this application because the resulting high level of wetting effectively protects the fibers and reduces interfiber wear that results in fiber breakage. Example 17 Following the procedure of Example 1, using PET having a melt viscosity of 3 Ns / m ² at 280 ° C., approximately 1.4 mm thick × 6 mm wide.
A tape formed at a linear velocity of about 0.2 m / min with a cooled sizing die of.

Not all commercial glass fibers are ideal for pultrusion using thermoplastics.
The most important difference lies in the size system used. Several commercially available grades were compared, along with a study of the effect of crystallinity. At the time of production, the pultruded product was amorphous, but it was easily crystallized by heating to 150 ° C. In Table 9 below, all samples using different glasses are compared at the same weight fraction of 64% by weight glass fiber.

[0080]

[Table 9]

A crystalline morphology that provides high stiffness is preferred in many applications, but the shear stress between layers (ILSS)
It is important to keep high values of, preferably higher than 20 MN / m ² . Example 18 High performance composite materials are often needed to enable use at high temperatures. Using a material containing 64% by weight of glass E used in Example 17 in PET, the properties as set forth in the following table were measured at elevated temperatures for crystalline pultrusion materials.

[0082]

[Table 10]

Example 19 Hot water is a common aggressive environment where the composite material is required to retain its properties. A sample based on 64% by weight of the glass fiber E used in Example 17 was pultruded with PET and immersed in a 95 ° C water bath for various times. The samples were tested both amorphous and crystalline. Properties deteriorated over time, and interlaminar shear strength (ILSS) was the most sensitive property.

[0084]

[Table 11]

In some other glass systems, interlaminar shear strength deteriorated to less than 10 MN / m ² after 4 hours of exposure. Example 20 Fatigue resistance is an important factor in the use properties of composite materials. A sample of a well-moistened pultruded article was prepared based on a material containing 64% by weight of the glass fiber E used in Example 17 in PET. The samples were subjected to a bending test to study the stress / strain relationship at 23 °.
The results obtained are given in the table below.

[0086]

[Table 12]

The sample had a linear elastic limit at 1% strain. The sample was bent at a rate of 1 cycle / 2 seconds using a 70 mm span in a 3-point bend. The number of cycles was recorded for significant damage to be induced (as judged by whitening of the pultrusion). The results obtained are given in the table below.

[0088]

[Table 13]

The samples were strained at 0.1% strain and the properties of the samples were evaluated after different histories. The results obtained are given in the table below.

[0090]

[Table 14]

These tests also included evaluating samples with surfaces that were under tension during the fatigue history in both compression and tension. No difference was observed in these two modes. The properties of the pultrusions were not affected by this fatigue history. Example 21 A tape sample with a thickness of approximately 1.4 mm x a width of 6 mm was prepared using PE.
The material containing the glass fiber used in Example 17 in T was prepared as the main component. The glass content was changed. In all cases, the pultrusions were transparent.

[0092]

[Table 15]

Example 22 High linear velocities are highly desirable for economical production. P
6 of glass fiber D used in Example 17 during ET
A pultrudate containing 9% by weight was formed by drawing the pultrusion through a molten bath containing 5 spreader bars. Wet pultrusions were obtained at the following rates and their properties were measured in bending.

[0094]

[Table 16]

Example 23 A pultrusion was made from the material containing glass fibers E used in Example 17 in PET at 280 ° C. using a single spreader. The viscosity of the resin was changed.
With the resin of very low viscosity, some resin was squeezed from the pultrusion during the molding stage, where the pultrusion was compressed to a width of 6 mm x a thickness of 1.4 mm. Linear velocity 0.2
It was fixed at m / min. The pultruded parts were bend tested in both amorphous and crystalline forms. The crystalline morphology was obtained by heating the sample to 150 ° C. for a short time.

[0096]

[Table 17]

As is evident from the above results, the very low viscosity samples provided useful properties in the amorphous state, but upon crystallization the properties deteriorated. At high viscosities, the glass was poorly wet (and thus gave a low resin concentration). Example 24 The tape of glass fiber E used in Example 17 is
By pultrusion on a single spreader (in PET with a melt viscosity of 3 Ns / m ² at 280 ° C.) and mixing well wetted, 6 mm wide, but different amounts of glass, Tapes of varying thickness were obtained. The sample tested was amorphous.

[0098]

[Table 18]

Example 25 Glass fibers having different diameters were pultruded with PET. The samples tested in amorphous had the following properties.

[0100]

[Table 19]

Example 26 The glass fiber E used in Example 17 is treated with polyethersulfone having a melt viscosity of 8 Ns / m ² at 350 ° C. in a single spreader system at 0.2 m / min. Impregnation was performed at a linear velocity of. The following properties were obtained.

[0102]

[Table 20]

Example 27 Carbon fiber was impregnated at 0.2 m / min in a single spreader pultrusion apparatus using PEEK having a melt viscosity of 30 Ns / m ² at 380 ° C. A rod with a diameter of 3 mm containing 60% by weight of carbon fibers was formed. Example 28 Conventional glass-filled PET (intrinsic viscosity 0.7
A blend was prepared from short fiber compound made by extrusion compounding with 5 of PET) and chopped into 10 mm pultruded parts (manufactured according to Example 3).
Injection molding of these blends, thickness 1.5mm x width 1
Filling from 0mm rectangular side gate, diameter 114
A disc having a thickness of 3 mm and a thickness of 3 mm was formed. These samples were exposed to impact in an instrumented drop weight impact test and the failure energy recorded.

[0104]

[Table 21]

All samples were filled into molds with similar ease. Because the polymer used to make the pultrusion was of lower molecular weight than the polymer used to make the short fiber blend, and this low molecular weight polymer offset the increased flow resistance due to long fibers Because. The results clearly show an increase in the failure energy of the long fiber filler material despite the low molecular weight of the polymer, which is usually expected to contribute to brittleness. Especially, the test No.
2 and No. 4 and the same total weight% of fibers should be compared.

Further, the molded product of the short fibers is torn when an impact is applied to cause a sharp plastic piece to fly off.
It was observed that when more than half of the weight fraction was long fibers, the moldings broke in a safe manner and all the broken pieces remained bonded to the main part. Ashing the molding after testing revealed that many of the long glass fibers retained most of their original length. Significantly more than 50% by weight of the original length of fibers in the molding was greater than 3 mm.

The samples were also evaluated for flexural modulus, anisotropy ratio, Izod impact strength, and intrinsic viscosity (IV) of the polymer in the molding. The values in Table 22 below indicate reduced anisotropy and good notched impact strength for short fiber products.

[0108]

[Table 22]

Example 29 Fourteen tapes of continuous carbon fiber (carbon fiber supplied by Courtland, labeled XAS), each containing 6000 individual filaments, were drawn at a speed of 25 cm / min. The stationary guide bar of the series was pulled over to form a band about 50 mm wide having a tension of about 100 pounds (45.4 kg). When the fibers were guided into an abutting relationship, they were pulled on a single fixed heated cylindrical bar of diameter 12.5 mm. The temperature of the bar was maintained at about 380 ° C. A powder of polyetheretherketone having a melt viscosity of ²⁰ Ns / m ² at this temperature was fed into the nip formed between the band of carbon fibers and the fixed roller. The powder melted rapidly forming a pool of melt in the nip, which melt impregnated a band of fibers passing over a roller. The construction was passed over and under five additional heated bars without adding additional amounts of polymer. It contains 58% by volume of carbon fibers and has a thickness of 0.
A carbon fiber reinforced sheet of 125 mm was produced. The product was found to have the following properties.

Flexural Modulus 130 GN / m ² Flexural Strength 1400 MN / m ² Interlaminar Shear Strength 90 MN / m ² Example 30 The procedure of Example 29 was followed. In this example, 360 ° C
A polyether sulfone having a melt viscosity of 3 Ns / m ² in was used to produce a reinforced product containing 40% by volume of carbon fiber. Roller temperature is about 36
Maintained at 0 ° C. The product had a flexural modulus and flexural strength of 700MN / m ² of 80GN / m ^2.

Example 31 The procedure of Example 29 was followed. In this example, 360 ° C
In Commercial having a viscosity of 800 ns / m ² to available polyethersulfone PES 200P (Imperial
Available from Chemikacal Industries PLS)
It was used. The roller temperature was maintained at about 360 ° C. A product containing 44% by volume of carbon fiber was produced. The product had the following properties.

Flexural Modulus 60 GN / m ² Flexural Strength 500 MN / m ² Interlaminar Shear Strength 25 MN / m ² Example 32 The general procedure of Example 29 was followed. In this example, an impregnated sheet was made using 14 tapes of continuous carbon fiber ("Coultaulds" XAS, 6K tow) and polyetheretherketone having a melt viscosity of 30 Ns / m ² at 370 ° C. In the device, each diameter is 12.
Five cylindrical bars of 5 mm were heated to 380 ° C. 1
The four tapes were pulled under tension to form a band 50mm wide, which was passed through the adjustable nip formed by the first two bars with the ordinate horizontal. This band was subsequently passed under and over three additional heated bars with the vertical axis also horizontal. The first two bars were used to form a nip so that the polymer could be fed to both sides of the band. To prevent polymer spillage, two retaining metal sheets were placed in contact with and along the length of the two heated bars to form a feed trough. Polymer powder was fed to both sides of the band passing through the first two heated bars. The powder melted rapidly forming a pool of melt in two nips formed between the sides of the band and each heating bar. Adjusting the gap between the first two bars, the carbon fiber was coated with polymer when the pulling speed was 0.5 m / min, and the resulting impregnated tape contained about 60% by weight of carbon fiber. It contained 40% by weight of polymer. It has been found that adjusting the fiber content can be achieved in several ways.

1. 1. Change the nip gap, 2. changing the pre-tension, 3. Change the number of filaments supplied to the nip, 4. changing the feed rate of the powder, Changing the temperature of the bar in the nip (for the resin used in this example the preferred temperature range was below 400 ° C. for decomposition and above 360 ° C. for the onset of crystallization), 6. Change the pulling speed. The tape thus formed appeared well-wetted and was about 0.1 mm thick.

Example 33 The tape described in Example 32 was cut to a length of 150 mm and stacked in a matched die compression molding machine. The molding machine was heated to 380 ° C. in a conventional laboratory press and compressed so that the moldings received a pressure of 2-5 × 10 ⁶ N / m ² . The molding was held at that pressure for 10 minutes (it took half the time for the mold and sample to reach equilibrium temperature) and then cooled to 150 ° C. under pressure before being removed from the press. The cooling step took approximately 20 minutes. The mold was cooled to ambient temperature and the molding was removed.

Moldings having a thickness in the range of 0.5 mm (4 plies) to 4 mm (38 plies) were formed as described above. During the molding operation, a small amount of polymer was squeezed out of the mold as a flash so that the molding contained 62% by weight of carbon fibers compared to 60% by weight in the original tape.
The moldings were then sawed with a diamond wafer saw to form a sample suitable for mechanical testing by the bending technique. The following results were obtained.

[0116] specimen of electrolyte span / depth ratio value flexural modulus 70: 1 130 GN / m ² Flexural modulus 30: 1 115 (6) GN / m 2 Flexural strength 30: 1 1191 (55) MN / M ² Bending strength in lateral direction 5: 1 98 (11) MN / m ² Shear strength between layers 5: 1 81 (4) MN / m ² (Numbers in parentheses indicate standard deviation) Example 34 Using the same equipment as in Example 32, some less wettable tapes were made by using less feed in some parts of the tape and more feed in other parts.
The total fiber content of the tape was the same as in Example 4, but much of the released fiber appeared on the surface of the tape and other areas were resin rich.

The tapes were stacked and molded as described in Example 33, taking care that the less wetted areas of one tape were located adjacent to the resin-rich area of the next tape. . Visual inspection of the molding left a substantially non-wettable area and the released fibers could be easily pulled from the surface. The mechanical properties of these moldings were inferior to those found in Example 33, and in particular the interlaminar shear strength varied and 10 MN
Low values of / m ² (compared to 81 for well-wetted samples) were common.

As this example shows, wetting of the fibers occurs predominantly during the impregnation stage and not during the secondary molding stage. However, it is believed that higher pressures and longer residence times could achieve some wetting. Example 35 The tape prepared in Example 29 was torn to give a thickness of about 15 mm.
Width tapes, and these tapes in tabby weave (as described in the Encyclopedia Bricanica Textiles section)
Was woven into a sheet approximately 150 mm square.

Example 36 The single woven sheet described in Example 35 is used in Example 33.
Was compression molded as described in Example 1 except that the molding was simply performed between aluminum sheets with the sidewalls unconstrained.
The molding was a flat sheet with a thickness of 0.2 mm. In an additional experiment, five woven sheets as described in Example 7 were layered together so that each layer was oriented ± 45 ° with respect to the layers above and below it. This laminate was compression-molded without constraining the side wall to form a sheet having a thickness of 1 mm. A 135 mm diameter disc was cut from this sheet and the stiffness and strength of the disc was measured by C.I. J. Hooley and S.H. Technology described by Turner (Mechanica)
l Testing of Plastics, Inst
itute of Mechanical Engineering
eers, June / Jully 1979, Autom
It was measured using a disk bending test and an automated falling weight impact test according to the Active Engineer).

[0120] bending stiffness of the plate had a maximum value and the minimum value of the 36GN / m ² of 50GN / m ^2. The impact resistance of the sheet was as follows: initial energy 1.7 (0.3) J failure energy 6.6 (1.1) J (standard deviation in parentheses) line of maximum stiffness. A sample with parallel sides cut along it was measured in a normal bending test with the following results.

Flexural Modulus 51 GN / m ² Flexural Strength 700 GN / m ² Example 37 Disks with a diameter of 135 mm and a thickness of 1 mm were prepared according to the procedure of Example 36, and 3 J of 3 J distributed evenly over the surface of this disk. It was subjected to 19 shocks. These impacts caused some delamination, but the damaged moldings remained cohesive.

The damaged disc was then reshaped and then tested as described in Example 36. The following results were obtained. Damaged and reformed Original shape (Example 5) Bending rigidity (maximum) 51GN / m ² 50GN / m ² Bending rigidity (minimum) 37GN / m ² 36GN / m ² Impact initial 1.9 (0 .1) J 1.7 (0.3) J Impact damage 6.5 (2.8) J 6.6 (1.1) J (standard deviation in parentheses) As can be easily understood, There is no significant difference in the above results.

As this example shows, after partial damage,
Nature fully regenerates. Example 38 A damaged disk prepared as in Example 37 was ruptured with 5 impacts using the instrument drop weight impact test.
The damage was localized to a region that was not much larger than the cross section of the impactor, and all the fractured parts remained bonded to the body of the molding.

Then, the destroyed molded product is remolded,
The impact test was then carried out, taking care to direct the new impact to the previously destroyed spot. The following results were obtained. Initial energy 1.8 (0.4) J Failure energy 4.6 (0.8) J (standard deviation in parentheses) By comparing with the results of Examples 33 and 34, the above results show that It shows that in bad cases, almost 70% of the original strength can be recorded.

Example 39 Diameter 135 mm made according to Example 36, thickness approximately 1
mm disc heated to 380 ° C, then 200 mm in diameter
Was placed in half of the normal temperature hemispherical female mold. Half of the male mold of this mold was pressed down by hand to form a hemispherical part having a radius of curvature of 100 mm. Portions up to about 100 mm in diameter (with a solid angle of about 60 ° from the center of the sphere forming a part) fit the double curvature well, but some waviness occurred outside this region.

Example 40 A woven sheet was prepared from 5 mm wide tape using 5 satin weaves (described in the Britannica Encyclopedia Textiles section). In the dry state, this fabric gave a doubly curved surface a very good composition and did not form pores in the fabric. Manufactures a five-layer quasi-isotropic sheet,
It was then molded as described in Example 36. This 1mm
Sheets of the following thickness were then heated to 380 ° C. and molded against various cold surfaces including: Right angle, cylindrical surface with radius of curvature 2.25 mm, spherical surface with radius of curvature 3.15 mm.

Good agreement was obtained in cases 1 and 2 above. For double curvature, stretch from the center of the sphere 6
Good agreement was obtained up to a solid angle of 0 ° (which is similar to the experiment of Example 39, but at a tighter radius of curvature with respect to the thickness of the sheet). The largest structures require only a gentle double curvature, but a tight weave requires a narrow weave, which is preferred over wide tabby weaves, especially in satin weaves, according to the general experience of the textile industry.

Example 41 One 40 mm square material was woven from a tape having a width of 2 mm and a thickness of 0.1 mm (tabby weave). The formability of a sheet of this material was compared to that of the wide tape fabric described in Example 35. The narrow tape could easily adapt to shape changes.
Molded sheets formed from these two fabrics appeared superficially similar in nature.

It is believed that narrow tapes may actually be used for the purpose of using conventional textile techniques. Example 42 The tapes formed in Example 32 were stacked to try to form a multilayer composite with each layer having a different orientation.
Since the tape was not "sticky" at room temperature when freshly formed, the layers tended to move with respect to each other during the placement and molding operations, so the fibers did not orient in the designed configuration in the final molding. It was This problem was partially overcome by locally tacking the layers together with a soldering iron. When molded in this manner, the sheet had to be molded by constraining the sidewalls to prevent the fibers from flowing laterally and disturbing the pattern of the designed orientation.

In contrast, woven sheets are convenient and easy to handle, and the interlocking tissue itself prevents lateral movement of the fibers, so molding is performed without constraining the sidewalls. I was able to. The ability to form a preferred sheet without constraining the sidewalls is particularly advantageous when considering the production of continuous sheets by methods such as double band pressing.

Example 43 The woven sheets of Example 35 were stacked and molded to form sheets of different thickness, each layer being at ± 45 ° with respect to the layers above and below it. The impact behavior of these sheets was determined by an instrumentation drop weight impact test. The results obtained are given in the table below.

[0132]

[Table 23]

Example 44 Polyethersulfone "Vi" was prepared according to the procedure of Example 32.
ctrex "200P and carbon fiber (Courtau
lds XAS, N.I. Size) to tape.
This polymer has 800 Ns / m ² at 350 ° C., and 40
It had a melt viscosity of 100 Ns / m ² at 0 ° C. The spreader was controlled at about 370-380 ° C and the pulling speed was 0.2 m / min. The tape did not wet as well as described in Example 32 due to the high viscosity of this resin. The resin content was increased slightly so that the final tape contained 50 wt% carbon fiber and 50 wt% resin.

A sample was formed as described in Example 33 to form a uniaxially oriented sheet having the following properties: Flexural modulus 60 GN / m ² Flexural strength 500 MN / m ² Transverse bending Strength 20 MN / m ² Interlaminar Shear Strength 26 MN / m ² The tape was then woven according to Examples 35 and 36,
The sheets were laminated and molded to form a sheet having a thickness of approximately 1 mm and having the following properties: Bending rigidity (maximum) 24 GN / m ² Bending rigidity (minimum) 21 GN / m ² Impact energy (initial) 2 .9 (0.3) J Impact Energy (Failure) 7.1 (0.3) J (standard deviation in parentheses) Reformed broken sheet and sample at same spot as original impact damage Be careful not to shock
Retested.

The flexural rigidity of the reformed sheet was 10% lower than that of the original sheet, but the impact resistance was reduced to 60% of its original value. Example 45 Polyethersulfone having a melt viscosity of 8 Ns / m ² at 350 ° C. was used to impregnate a tape of carbon fibers. The carbon fibers were previously sized with 5% by weight of polyethersulfone by the solution sizing method.
This sample was impregnated by pulling it over four spreaders heated to 350 ° C. at a speed of 0.2 m / min. The final composite material contained 47% by weight carbon fibers. A sample was molded and tested according to Example 30 with the following results: flexural modulus 85 GN / m ² flexural strength 680 MN / m ² interlaminar shear strength 50 MN / m ² This sample was run. Although made from a lower molecular weight polymer than that used in Example 44, it is noted that the composite has excellent properties.

Example 46 A glass roving made of polyethylene terephthalate (2
Impregnation was carried out at 70 ° C. with a melt viscosity of 3 Ns / m ² ) according to the procedure described in Example 32, but using a 280-300 ° C. bar. Up to 80% by weight of glass fibers were satisfactorily incorporated to give excellent wetting. At 60% by weight glass, a linear velocity of 5 m / min was easily achieved for a tape with a thickness of 0.1 mm.

Example 47 A glass roving was impregnated with polypropylene having a melt viscosity of 10 Ms / m ² at 270 ° C., using the same equipment as in Example 32, but maintaining the bar at 270 ° C. Very wet 0.1 mm at 50% by weight of glass fiber
Thickness of tape was obtained, which was especially useful for overlapping tubes and other parts made from polypropylene.

Example 48 Contains residues of hydroxynaphthoic acid, terephthalic acid and hydroquinone and has a melt viscosity at 320 ° C. of 7 Ns /
m ² is a thermochromic polyester, carbon fiber (“Ce
lion "6K and 3K tow). The equipment was identical to that described in Example 32, except that the bar was maintained at 320 ° C. 0.1 mm containing 62% by weight carbon fiber. The thick tape had an excellent appearance.

Example 49 Examples 32-38, including certain materials with excess resin.
Various pieces of scrap material produced from B.S.A. were broken and fed to a conventional screw extruder and compounded to form granules. The granules contained carbon fibers with a thickness of up to 0.25 mm. These granules, according to the usual molding technique,
Injection molded under standard operating conditions for filled PEEK. The molded product had the properties as shown in the following table. In addition, these properties, manufactured by ordinary compounding work,
Compare to the properties of the best available commercial grade carbon fiber filled PEEK: Scrap formulation Weight% of best commercial grade carbon fiber 55 30 Modulus 32 GN / m ² 13 GN / m ² Tensile strength 250 MN / m ² 190 MN / m ² surface quality excellent excellent As is apparent from this example, the product of the invention can be converted into a product for common processing methods, which product can be obtained by the state of the art. Better in some ways than things. Also, scrap from various long fiber operations, such as sheet production, lamination, and filament winding, can be reclaimed into high performance materials. The renewable nature has great economic implications when working with expensive raw materials such as carbon fiber.

Example 50 The optimum tension during roving when operating according to the method of Example 29 is determined by measuring the tension in individual rovings containing 6000 filaments before impregnation and in the tensioning stage. Did (14
Book roving was used in Example 29, and the working tension will actually be 14 times the value below). The values below were determined to be the minimum working tension (case 1) and the maximum working tension (case 2) for the particular roving, polymer type and equipment used. Using tension values less than those of Case 1, there were fiber misalignments and tears in the tapes produced. With tension values higher than those in Case 2, fiber wear was observed and released fibers accumulated on the band. Although different values were obtained for different sets of conditions (roving, polymer type, etc.), they could be easily optimized to give excellent quality products.

Tension before impregnation Tensile tension Case 1 0.14 kg 2.4 kg Case 2 0.37 kg 3.8 kg

[0142]

As is apparent from the above description, according to the present invention, in the fiber reinforced pellet structure, (a) the fiber content can be increased, (b) the wetting of individual filaments wetted by the impregnating resin or polymer. It is possible to maintain the agglomeration state of the resulting pellet structure after shredding the structure which is a continuous product. D) Making the pellet structure a molded product In this case, it is possible to obtain effects such that the appearance of the obtained molded product becomes good, and (e) when the pellet structure is used as a molded product, there is no loss in filament length.

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[Procedure amendment]

[Submission date] October 27, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title of invention Fiber-reinforced pellet structure for thermoforming

[Claims]

[Equation 1] Of less than 15% has the form of pellets chopped into a continuous structure, and the individual filaments contained in the pellet structure are substantially separated by the thermoplastic polymer in a melt pultrusion process. And the pellet structure has the form of individual filaments in which the filaments in the molded product obtained by injection molding are randomly dispersed. A fiber-reinforced pellet structure for thermoforming, characterized in that at least 50% by weight of the filament can be shaped into a shaped article having a length of at least 3 mm.

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to thermoformed fiber reinforced pellet structures, and more particularly to thermoformed fiber reinforced pellet structures containing a thermoplastic polymer and reinforcing filaments.

[0002]

2. Description of the Related Art Conventional production of fiber-reinforced pellet structures is carried out, for example, by a solvent impregnation method, a melt impregnation method or the like. The melt impregnation method includes, for example, a melt drawing method. The melt pultrusion method, or abbreviated pultrusion method, can be carried out by passing a tow or roving of glass fibers through a bath of low viscosity thermosetting resin to impregnate the fibers. The structure thus obtained is subsequently cured by heating. Although such methods have been known for at least 10 years, they have not been used commercially to any extent in the manufacture of thermoplastic resin impregnated structures. The reason for this is that it is difficult to wet the fibers when drawn through a viscous molten resin. The resulting product has unacceptable properties as a result of poor wetting.

The efficiency of a particular method is that it wets the fiber and thereby provides the basis for maximizing the very high levels of physical properties inherent in continuous fibers, such as glass fibers. , Can be evaluated by measuring the extent to which a product having a flexural modulus that reaches the theoretically attainable flexural modulus is provided.

The theoretically achievable flexural modulus is calculated using the simple rule of mixtures as follows: E _L = V _f E _f + V _m E _m where E _L is the composition Is the vertical modulus,
V _f is the volume fraction of the fiber, E _f is the flexural modulus of the fiber, V _m is the volume fraction of the matrix polymer, and E _m is the flexural modulus of the matrix polymer. .

However, when a melt of a conventional high molecular weight thermoplastic polymer is used for impregnation of continuous roving, a high level of flexural modulus cannot be obtained. For example, US Pat. No. 3,993,726 is an improved method of impregnating continuous rovings under high pressure in a crosshead extruder, drawing the rovings through a die, and cooling and molding the rovings to produce a molded article. Disclosed method. The product obtained with polypropylene is shown in Example 1 and has a glass fiber content of 73% by weight of only about 6 GN / m ² , ie 20% of the theoretically achievable value. It is described that it shows only the flexural modulus.

[0006]

DISCLOSURE OF THE INVENTION The object of the present invention is to realize the above-mentioned problems of the prior art.
Especially in a fiber reinforced pellet structure, the content of fibers is high, the degree of wetting of individual filaments wetted by the polymer melt is high, and the appearance state of the molded article obtained when the molded article is manufactured from the pellet structure It is an object of the present invention to provide an improved fiber-reinforced pellet structure which has a good quality and does not cause a loss in filament length in a molded product.

[0007]

According to the invention, as a means for achieving the above-mentioned object, a thermoplastic polymer having a length of 3 to 100 mm and at least 30
A pellet structure comprising, by volume, parallel reinforcing filaments, wherein the pellet structure has a void content defined by the following formula (I):

[0008]

[Equation 2]

Has the form of pellets chopped into a continuous structure having a content of less than 15%, and the individual filaments contained in the pellet structure have the thermoplastic polymer in the melt pultrusion process. That is substantially wetted by, and that the pellet structure has the form of individual filaments that are injection molded to randomly disperse the filaments in the resulting article after molding. And at least 5 of the filaments
There is provided a fiber-reinforced pellet structure for thermoforming, characterized in that 0% by weight can be molded into a molded article having a length of at least 3 mm.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to its preferred embodiments. In the following description, in order to facilitate understanding of the present invention, a fiber-reinforced structure, a fiber-reinforced composition, which the present inventors have invented together,
Then, the fiber-reinforced pellet structure of the present invention will be described in connection with the description of the fiber-reinforced molded article.

The present inventors have recently found out that
Materials having flexural modulus levels approaching theoretically attainable levels are those made by the continuous process and contain at least 30% by volume of the structure of reinforcing filaments extending in the machine direction of the structure, and ASTM D79
Fiber comprising a thermoplastic polymer and a reinforcing filament, characterized in that the flexural modulus of the structure measured according to 0-80 is at least 70%, preferably at least 80% of the theoretically attainable flexural modulus. It is a reinforced structure. The interlaminar shear strength of these structures is 10MN / m
Greater than ² , preferably greater than 20 MN / m ² . The preferred thermoplastic polymers for use in this invention are crystalline polymers having a melting point of at least 150 ° C and amorphous polymers having a glass transition point of at least 25 ° C. For optimum rigidity, the thermoplastic polymer should have a flexural modulus of at least 1 GN / m ² , preferably at least 1.5 GN / m ² .

The fiber-reinforced structure described above can be produced by a variety of methods which allow good wetting of continuous, aligned filaments. In one of these methods, the melt viscosity is less than 30 Ns / m ² , preferably 1
It consists of drawing a plurality of continuous filaments through a melt of a thermoplastic polymer which is -10 Ns / m ² and wetting them with the molten polymer, said filaments being aligned along the direction of drawing. A method for producing a fiber-reinforced composition is provided. If desired, the impregnated filaments may be consolidated into a fiber reinforced polymer structure. The viscosity of thermoplastics changes with shear rate and decreases from a near constant value at low shear rates. For purposes of this application, reference is made to viscosity at low shear rates (commonly referred to as Newtonian viscosity). This viscosity is conveniently measured using a capillary viscometer using a 1 mm diameter and 8 mm long die, and melt viscosity is measured at shear stresses in the range 10 ³ to 10 ⁴ N / m ² .

Surprisingly, the fact that such polymers have a lower molecular weight than is usually considered suitable in the field of thermoplastic polymers to achieve satisfactory physical properties. Despite this, the reinforced composition has very good physical properties. When making a reinforced thermosetting polymer composition by the pultrusion process, the viscosity of the thermosetting prepolymer in the impregnation bath is typically less than 1 Ns / m ² for good wetting of the fibers. Is. The reason why this low viscosity value can be used is that the prepolymer is subsequently converted to the solid form by thermosetting. In contrast, thermoplastic polymers are usually fully polymerized solid materials and are obtained in liquid form only by heating and melting the thermoplastic polymer. However, the melt viscosity of conventional high molecular weight polymers with acceptable physical properties is typically above 100 Ns / m ² . It is not possible to obtain adequate wetting of the fibers with the pultrusion method using such high viscosity melts. Although the melt viscosity can be lowered to some extent by increasing the temperature of the melt, the decrease in viscosity that can be achieved at a temperature below the decomposition temperature of the thermoplastic polymer is usually insufficient.

Low enough to give a sufficiently low melt viscosity
Using a thermoplastic polymer with a high molecular weight,
What is amazing when properly wetting fibers in the form method
In addition, high strength products can be obtained. Therefore, the melt viscosity
30 Ns / m² Smaller, preferably 1-10 Ns / m ² 
Through the melt of the thermoplastic polymer, which is between
Pull continuous filaments to melt them
Obtained by wetting with a molten polymer, in which case it
These filaments are aligned along the pulling direction.
A fiber-reinforced thermoplastic composition is provided, characterized by
It Fiber reinforced structures produced are less than 15%, preferred
It should have a void content of less than 5%.

The term "continuous fiber" or "plurality of continuous filaments" means that, under the processing conditions employed, it is of sufficient strength to pull through the molten polymer without breaking at a frequency that renders the processing infeasible. By any fiber product, such that the fibers have a sufficient length to form rovings or tows. Suitable materials are glass fibers, carbon fibers, jute and high modulus synthetic polymer fibers. In the latter case, it is important to satisfy the condition that the polymer fibers have sufficient strength to be able to be pulled in the polymer melt without causing disruption to the process. In order to have sufficient strength to be pulled through the impregnating system without breaking, the majority of the continuous fibers of the fiber product are oriented in one direction, and the fiber product has a majority of the continuous fibers. It should be aligned and pulled through the molten polymer.
Textiles such as mats composed of randomly arranged continuous fibers are not suitable for use in the present invention unless they form part of a fiber structure in which at least 50% by volume of the fibers are aligned in the pulling direction. Appropriate.

The continuous fibers can be in any form with sufficient integrity to be drawn through the molten polymer, but conveniently, substantially all of the fibers are aligned along the length of the bundle. A bundle of individual fibers or filaments (hereinafter referred to as "roving"). Any number of such rovings can be used. In the case of commercially available glass rovings, each roving can consist of up to 8000 or more continuous glass filaments.
Carbon fiber tapes containing up to 6000 or more carbon fibers may be used. Fabrics woven from rovings are also suitable for use in the present invention. The continuous filaments may be treated with any conventional surface sizing, especially those designed to maximize the bond between the fibers and the matrix polymer.

In order to achieve the high levels of flexural modulus enabled by the use of the present invention, it is necessary that as much of the surface of the continuous filament as possible be wetted with molten polymer. Thus, where a fiber is composed of multiple filaments, the surface of the individual filaments that make up the fiber must be wetted for optimal effect. Where the filament has been treated with a surface sizing or fixing agent, the polymer will not come into direct contact with the surface of the fiber or filament due to the interposition of the sizing agent. However, as long as good adhesion is achieved between the fiber and the size and between the size and the polymer, the product of the invention has a high flexural modulus and the size is generally obtained. Will enhance the nature.

The thermoplastic polymer used in the above process has a melt of less than 30 Ns / m ² , preferably 1
It can be any polymer that melts to form a cohesive mass as long as it has a viscosity of less than 0 Ns / m ² . In order to achieve acceptable physical properties in the reinforcing composition, the melt viscosity is preferably above 1 Ns / m ² .
As indicated above, the choice of polymer in the required melt viscosity range depends primarily on the molecular weight of the polymer. Examples of suitable polymers are thermoplastic polyesters, polyamides, polysulfones, polyoxymethylene, polypropylene, polyarylene sulfide, polyphenylene oxide / polystyrene blends, polyetheretherketone and polyetherketone. Various other thermoplastic polymers can be used in the method of the present invention, but polymers such as polyethylene will not provide such high strength compositions.

In the method of impregnating the fibers of the roving, it is necessary to maximize the penetration of the melt into the roving, in addition to using a polymer of suitable melt viscosity to achieve the proper wetting. is there. This applies the static charge to the rovings to the individual constituent fibers, for example the rovings before they enter the molten polymer, or
Alternatively, and preferably, while the roving is present in the molten polymer, it can be done by spreading the roving and separating it into constituent filaments, separating as much as possible. This is conveniently accomplished by passing the roving under tension over at least one, and preferably several, spreader surfaces. Further enhancement of wettability by adding additional work to the opened and polymer impregnated fibers, for example by solidifying said opened fibers by drawing impregnated rovings from the melt through a die. Is obtained.
The die can have the desired profile for impregnating roving, or the impregnating roving can be passed through an additional sizing die while the polymer is still flowable. Surprisingly, it would be advantageous if the die were cooled to achieve satisfactory sizing and smooth passage through the die. When the impregnating roving is discharged from the bath in the form of a flat sheet, additional work can be added by passing the sheet between a pair of rollers.

The speed at which the roving can be pulled through the impregnation bath depends on the requirement that the individual fibers be properly wetted. This will depend, to a large extent, on the length of the passage through the bath of molten polymer, and in particular on the degree of mechanical enlarging action that the rovings will undergo in the bath. The speeds achievable with the method of the present invention are at least comparable to those achievable with the pultrusion process of thermosetting materials. This is because the pultrusion process is limited by the time it takes to complete the necessary chemical reaction after the impregnation step.

In one preferred embodiment, the spreader surface over which the roving is drawn to open the roving is for heating the spreader surface to a temperature above the melting point of the particular polymer to be used for impregnating the roving. Equipped with an external heat input section. By this means, the melt viscosity of the polymer in the local area of the spreader surface is
It can be maintained at a much lower value than that of the polymer in most of the impregnation bath. The advantage of this method is that a very small portion of the polymer can be heated to a relatively high temperature, which minimizes the risk of the major portion of the polymer in the bath degrading and results in a low impregnation viscosity. It is in. This results from the fact that the polymer feed into the bath is continuously replenished, so that it is possible for some polymers to remain in the bath for a period of almost unlimited duration during a given treatment period. The problem to do is greatly reduced. Therefore, some of the polymer present at the beginning of the treatment period may still be present in the bath at the end of the treatment period. Despite this long residence time in the bath, such polymers will experience a less severe thermal history than if the entire polymer in the bath were exposed to elevated temperatures to obtain a low viscosity throughout the bath. Let's do it.

A further advantage of the local heating method is that polymers with poor thermal stability can be used. further,
The lower degradation resulting from the lower total thermal history allows higher temperatures to be locally used due to the formation of lower viscosity melts, allowing higher molecular weight resins to be used. The supply of polymer to the impregnation bath can be in the form of a polymer powder which is melted in the bath by an external heating element or by a heated spreader surface placed inside, or alternatively The molten polymer can be fed to the bath using, for example, a conventional screw extruder. If the bath has a heated spreader surface, the polymer melt delivered from the extruder should be at the lowest temperature possible to minimize thermal decomposition. The use of melt feed is easy to start, has good temperature control, and especially when producing very thin structures,
It has the advantage that the formation of unmelted polymer agglomerates, which causes various processing problems, is avoided.

The impregnated fiber product can be drawn through a means for hardening the product, such as a sizing die. The temperature of this die has been found to have a significant effect on this method. It is expected that a thermal die should be used to minimize friction in the die and promote solidification, but it has been found that the die maintained at a temperature above the melting point of the polymer used. Causes an extraordinary sticky slip behavior as the product is drawn through the die. It has been found to be preferable to use a cooled die and to ensure that the surface temperature of the pultruded part entering the die is no more than 20 ° C. above the softening temperature of the polymer.
"Softening temperature" means the lowest temperature at which a polymer can be sintered. This can be accomplished by blowing air over the race in the passage between the impregnation bath and the die and / or by spacing the die from the impregnation bath. If the pultruded part is overheated, the polymer will be squeezed out as the product enters the die. This leaves deposits at the entrance to the die, and the deposits may accumulate and score the pultruded portion as it passes through the die. The pultruded part should not be cooled below the softening point of the polymer. Because it is too difficult to shape the product with a sizing die.

The dimensions of the fiber reinforced product can be varied as required. Thin sheets can be made by separating the fibers of rovings by passing a number of rovings over a spreader surface so that the fibers form a band in abutting relationship. When the die is used to compact the fibers, the structure will take the form of a sizing die cross section. This allows any required thickness, eg 0.25.
Articles with a thickness or linear profile of mm to 50 mm can be formed. Sheets having a thickness of 0.05 mm or less can be produced when the means for compacting includes a nip formed from at least one pair of rotating rollers.

In a further method of producing fiber-reinforced structures, it has been found that satisfactory wetting can be achieved even when the thermoplastic polymer used has a melt viscosity of significantly above 30 Ns / m ² . Therefore,
Tensioning and aligning multiple continuous filaments to form a band of adjacent filaments such that a nip is formed on the heated spreader surface between the band and the spreader surface. Through, maintaining a supply of thermoplastic polymer at the nip, where the temperature of the spreader surface causes a polymer melt of a viscosity capable of wetting the continuous filament as it is drawn over it. A method is provided for making a fiber reinforced composition that is sufficiently high to form. The polymer melt at the tip of the nip preferably has a viscosity of less than 30 Ns / m ^2, but the high back tension on the filaments to be fed to the spreader surface ensures that impregnation of the polymer in the nip region is suitable. As a result, it is possible to produce impregnated bands at viscosities significantly higher than 30 Ns / m ² . Thus, this method provides a means of maximizing the molecular weight of the polymer that can be used in the thermoplastic polymer extrusion process.

In one embodiment of this method, continuous filaments are most suitably tensioned and aligned by pulling them from a roll or reel onto a series of spreader surfaces, such as the surface of a rod. It This allows the bundle of filaments to be spread as far as possible into the individual filaments under considerable tension. These filaments are guided to form bands of adjacent filaments as they pass over the heated spreader surface. The shape of the spreader surface and the contact angle between the filament band and the spreader surface should be such that a nip is formed between the band and the heated spreader surface. A powder of thermoplastic polymer is fed to the nip and the heated spreader surface is maintained at a temperature sufficient to melt the thermoplastic polymer. As the band passes over the heated spreader surface, the melt impregnates and wets the fibers of the band.

The method further comprises providing at least one additional heated spreader surface to form a second nip with the band of at least partially resin impregnated fibers with the spreader surface. This nip can be modified by allowing an additional feed of polymer to be impregnated into the band of fibers. The surface of either of the partially impregnated bands can also be used to form the working surface of the nip.

The amount of polymer in the reinforced structure is largely controlled by the tension exerted on the band and the length of the channels through which the band contacts the heated spreader surface. Thus, when the band is under high tension and is in substantial surface contact with the spreader surface so that the band is pressed hard against the spreader surface, the polymer content of the reinforced structure is low tension / short. Will be less than under the conditions of the contact passage.

The heated spreader surface and any subsequent heated or cooled surface used to improve impregnation or improve surface finish are preferably in the form of cylindrical bars or rollers. For example, the first impregnated surface can be a freely rotating roller, which is rotated by the band at the speed of the band so that the abrasion of the fiber prior to impregnation or sizing by the melt is minimized. Could be reduced to. It has been observed that loose fiber build-up on the band takes place through this system when the first roll rotates (freely or driven) in the direction of fiber movement up to the fiber speed. This self-cleaning action is particularly effective in preventing the accumulation of fibers on the first roll which can divide the band.
After the band has taken up some of the melted polymer, preferably on the other side of the band is provided additional melted polymer by a second freely rotatable heated surface,
The fibers are much less prone to abrasion and can be subjected to treatments to improve the wetting of the fibers.
Thus, the polymer-containing band can be passed over at least one roller driven in the direction opposite to the direction of movement of the band to increase local work input to the band and maximize wetting. In general, the degree of wetting and the speed of the method can be increased by increasing the number of surfaces on which work input is present.

Another advantage that the method of forming a nip using a band of fibers can provide, as compared to methods that require the use of a bath of molten polymer, is to reduce the risk of degradation. Therefore, a relatively small amount of polymer is present in the nip between the band of fibers and the spreader surface, so that a large amount of polymer does not have to be kept at elevated temperature for an extended period of time. A scraper blade can be placed at the location where the polymer is fed to the nip to remove excess polymer that may accumulate and undergo thermal decomposition during processing.

When the product of the above process is required as a thin reinforced sheet, the product produced by impregnation in the nip is further passed by passing over or between additional heated or cooled rollers. It can be treated to improve impregnation or improve the surface finish of the sheet. Thin sheets tend to curl when one side contains more polymer than the other. This can be avoided by placing an adjustable heated scraper close to the last roller in the roller system to remove excess polymer on the surface of the sheet. The scraper bar should be at a temperature just above the melting point of the polymer. For example, in the case of polyetheretherketone, which reaches a temperature of about 380 ° C. in the impregnation zone, the temperature of the scraper bar should be about 350 ° C.

The impregnated band can then be further processed depending on the intended shape and purpose of the final product. The open filaments in the impregnated band can be drawn together, for example, through a die to give a profile with a thickness that is significantly greater than the impregnated band. A limited amount of molding can be performed on such a die to obtain a molded profile.

The impregnated product of the above-described process is made into a long piece for subsequent use in molding processes requiring continuous products, for rolling or subsequent molding. You can shred. The continuous strip can be used to make an article, for example, by wrapping the heat softened product around a former, or by weaving a mat from, for example, a tape or strip of the product. The impregnated product can be chopped into pellets or granules in which the aligned fibers have a length of 3 mm to 100 mm. These things are
It can be used in conventional molding or extrusion methods.

When using glass fibers, the fiber content of the product of the invention is at least 50% by weight of the product in order to maximize the physical properties of the product. The upper limit of the fiber content is determined by the amount of polymer required to wet the individual fibers of the roving. In general, it is difficult to achieve good wetting with less than 20% by weight of polymer, but good results show that 30% by weight of polymer is incorporated into a fiber reinforced composition using the method of the invention. Can be obtained by doing.

The product of the invention, formed by the method of impregnating adjacent bands of roving in the nip formed by the band and the heated spreader surface, comprises:
Usually, the impregnation system will be pulled as a band or sheet of material. This provides an intermediate useful for many applications. A thin band or sheet, ie 0.
Thicknesses less than 5 mm and greater than 0.05 mm are particularly useful and versatile.

The tape is woven using a tabby or satin weave, which terms are used in the field of textiles and are described in the "Weaving" section of the Encyclopedia Britannica. It is particularly useful in forming a finished article. The satin weave gives a particularly good product, as shown in the examples herein. Fabrics with very high performance are obtained with tapes produced according to the invention and having a width of at least 10 times the thickness. One important application is as a thin reinforced sheet, which consists of a ply of multiple reinforced sheets,
Can be used to form a reinforced article,
The reinforcement of each layer is then placed in the plane of the layer in the selected direction and the layers are compressed at a temperature sufficient to fuse the polymers of the layers. The layer can be used as a flat sheet that can be molded in a mold during or after the fusing step, or else wrapped or molded on a shaping mandrel and having the shape of the mandrel after the fusing step. An article can be obtained.

Producing a reinforced molded article by, for example, wrapping a reinforcing filament on a forming mandrel and sandwiching a layer of polymeric film between layers of filaments and subsequently fusing the polymeric film is known, for example. , As disclosed in British Patent No. 1,485,586. The present invention is superior to such methods. The main advantages are that the use of high-cost preformed polymer films can be avoided, the content of the polymer can be controlled by the tension of the band, thus avoiding the provision of films of various thicknesses, and Advantages derived from the continuous nature of the method of the invention.

The pultruded article of the present invention is also suitable for being chopped to an appropriate size to selectively reinforce the article molded from a polymeric material. At least one preformed element comprising a product according to the invention is placed in a mold to strengthen selected portions of the finished molding, and a polymeric material is molded around the in situ reinforcement to create a shaped article. To form.

The present invention not only allows the fiber reinforcement to be placed in a molded article to obtain the maximum effect on the stress the molded article is subjected to during use, but also to provide such high strength articles. It overcomes the processing problems encountered when manufacturing differently. In particular, this method has a melt viscosity of 1
It can be used to produce such reinforced articles by a high productivity injection molding process using common thermoplastic polymers of 00 Ns / m ² or higher.

In some applications, the preformed element may be
It is advantageous to use it at a temperature at which it is flexible so that it can be more easily placed in the mould, for example by wrapping a heat-softened preformed element around the mold insert. Will. The molding method used may be any method of forming a molded article in a mold from a polymeric material. The polymeric material may be a thermoplastic material that is introduced into the mold as a melt, as in the injection molding process, or as a powder, as in the compression molding process. The term "compression molding method" includes the method of compressing a polymer powder without melting and subsequently sintering this "green" molded article out of the mold.
The thermoplastic polymeric material that is molded in the mold is one or more monomers or moieties that are held in the mold until they are completely polymerized, for example under the action of heat or a chemical activator or initiator. It can also be induced by introducing a chemically polymerized medium.

The polymer molded around the preformed insert is preferably the same as, or at least compatible with, the polymer used to impregnate the preformed insert. The impregnated product obtained by the method described above may have particular utility in the case where the reinforcing fibers involved are chopped into pellets or granules having a length of at least 3 mm, preferably at least 10 mm. These products can be used in conventional molding processes such as injection molding and are superior to prior art products in the form of pellets. Because the length of the fiber in the pellet is
It is retained to a much greater extent than when using prior art products. This greater fiber length retention is believed to be a result of the greater protection provided to the individual reinforcing filaments in the products of the present invention, due to the superior wetting by the polymer resulting from the use of the foregoing method. Can be

This aspect of the invention is of particular importance. This is because it allows the reinforced article to be formed in a flexible operation, such as injection molding, which uses a screw extrusion process to melt and homogenize the feed material, and the fiber length is It is surprisingly highly retained and eventually improves its physical properties. The product of the invention thus makes it possible to obtain moldings from a molding process using screw extrusion, which moldings contain at least 50% by weight, preferably at least 70% by weight, of fibers having a length of at least 3 mm. To do. This is significantly longer than what would normally be obtained from commercially available fortified products. Another method for forming shaped articles by melting and homogenizing short length, ie 2-100 mm, reinforcement products of the invention is by calendering. For example, sheet products can be manufactured in this way.

The products of the invention suitable for injection molding can be used directly or blended with pellets of other thermoplastic products. These other products can be the same polymer but of higher molecular weight, or they can be different polymers, as long as the presence of different polymers does not adversely affect the overall balance of composition properties. Other products may be unfilled polymers or may contain particulate or fibrous fillers. Blends with conventionally produced reinforcing molding powders, i.e. materials containing molding powders containing reinforcing fibers up to about 0.25 mm in length, are particularly suitable. This is because short reinforcing fibers do not contribute as effectively as the long fibers provided by the product of the present invention, but can maintain a high content of reinforcing fibers throughout the blend.

The shredded shape of continuous pultruded articles is also very useful as a feedstock for the process described in co-pending British Patent Application No. 8101822.
In the method of this British patent application, the fiber reinforced molded article is
A composition comprising a curable fluid as a carrier for fibers of at least 5 mm length is passed through a die so that as the extrudate leaves the die it relaxes the fibers and causes the extrudate to expand, leaving Produced by forming a regularly dispersed open fiber structure and compressing the manufactured porous structure into a molded article while the carrier is in a fluidized state.

The term "curable" means that the fluid "solidifies" in a form such that it retains the fibers in the irregular orientation that occurs during extrusion. Thus, for example, the curable fluid is extruded in the molten state,
It can be a molten thermoplastic material that then solidifies by cooling until it freezes. Preferably, the expanded extrudate is extruded directly into the mold chamber which has a means of compressing the porous extrudate into a molded article,
Then, the extrudate is compressed or processed into a molded article before or after the extrudate is solidified.

Since the extrudates formed in this way contain irregularly dispersed fibers, only the orientation of the fibers in the molding is the result of the compression process. This method can be used with high fiber loadings, ie, greater than 30% by volume. Since fiber breakage rarely occurs, molded articles with extremely high strength can be obtained, measured in all directions of the product.

At least 5 m of pultrusion product of the invention
Pellets obtained by chopping to a length of m, preferably at least 10 mm, are advantageous. The upper limit of length is determined by the degree of problems encountered in the material feeding the extruder that melts the product. At least 50
Lengths up to mm can be used, but the advantage of large fiber lengths is partly compromised, as their length increases the amount of fibers that break.

In order to achieve proper wetting of the rovings, relatively low molecular weight polymers, eg 30 Ns /
below the m ^2, preferably it is necessary to use a polymer of melt viscosity of less than 10 ns / m ^2, and it is that should Odorokiroku having physical properties of high levels of such products is applied However, the present invention does not exclude subsequent processing steps such as increasing the molecular weight of the polymer in the composition by known methods. Such techniques include solid state polymerization in the case of condensation polymers, the use of cross-linking agents or irradiation techniques. When cross-linking agents are used to increase the molecular weight, it is necessary to mix them homogeneously in the composition. This can only be done if they are already present during the impregnation, but in such cases care must be taken that the crosslinkers are not activated before the completion of the wetting step.

[0049]

The present invention will be described in more detail below with reference to typical examples. It should be understood that the present invention is not limited to these examples. Example 1 Using a copolymer of polyethylene terephthalate in which 20% by weight of terephthalic acid has been replaced by isophthalic acid and having the intrinsic viscosity values listed in Table 1 below, in a bath at a temperature of approximately 290 ° C. A polymer melt was prepared. A roving of a glass containing 16000 individual filaments was drawn through the molten polymer over one spreader placed in the bath at a rate of 30 cm / min giving a residence time in the bath of 30 seconds. It was The impregnated rovings were drawn through a 3 mm diameter die in the bath wall and then cooled.

The melt viscosity and the intrinsic viscosity of the polymer in the polymer feedstock and in the fortified composition were measured. The wettability and void content of the fibers were evaluated by comparing the weight of the fully wetted length of the impregnated product with the same length of product of unknown wettability. The completely wet control material was obtained by pultrusion of a low viscosity melt at a very slow rate so that a completely transparent product was obtained. Thus, the completely wet standard was taken to be the sample that was made under conditions that were transparent and optimized the parameters suitable for wetting. Table 1 below
The value of the degree of wetting described in is derived from the following relational expression:

[0051]

(Equation 3)

Here, M ₀ , M ₁ and M ₂ are the same as defined above. The void content (%)
Can be obtained by subtracting the value of the degree of wetting from 100%, as indicated above. Product strength was evaluated by measuring the force required to bend and break a sample of 3 mm rods placed across a 64 mm span. The results obtained are listed in Table 1 below.

[0053]

[Table 1]

Example 2 The polymer used in Example 1 and having an intrinsic viscosity of 0.45 dl / g was evaluated over a range of melt temperatures and draw through rates. The results obtained are shown in Table 2 below.
Described in.

[0055]

[Table 2]

Example 3 PET having a melt viscosity of 6 Ns / m ² at 280 ° C.
The homopolymer was prepared as described in Example 1 with a diameter of 17
280 glass fiber composed of μm filaments
Used at 0 ° C., pultruded using a single spreader rod and a linear velocity of 30 cm / min to give a pultruded rod of approximately 3 mm diameter. The glass content of the product was changed by changing the number of strands in the roving fed to the bath. Flexural modulus and force at break were determined as a function of glass content using a 64 mm span. The results obtained are listed in Table 3 below.

[0057]

[Table 3]

These results show that the range is 50-65% by weight.
It is shown that the elastic modulus and the strength have an approximate plateau at the glass content of. Example 4 Conventional grade polypropylene has a viscosity above 100 Ns / m ² at lower shear rates and is not suitably processed by pultrusion. For example, the melt viscosity of "Propathene" HF11, a polypropylene homopolymer, is about 3000 Ns / m ² at 280 ° C. at low shear rates, and 2
It is about 10,000 Ns / m ² at 30 ° C. In order to prepare polymers suitable for pultrusion, "Propathen"
e "HF11 with 0.1% calcium stearate,
0.1% "Irganox" 1010 and 0.5%
"Luperco" 101XL ("Luperco"
101XL was an organic peroxide dispersed with calcium carbonate) to allow decomposition to occur. This formulation is 2 at 30 cm / min using a single spreader.
Pultruded at temperatures of 30 ° C and 290 ° C. Two
Wetting was poor at 30 ° C. (melt viscosity 30 Ns / m ² ). At 290 ° C (melt viscosity 17 Ns / m ² ),
Wetting was moderate.

Example 5 A sample of "Victrex" polyether sulfone having a relative viscosity of 0.3 was pultruded with the glass fibers used in Example 3 at 405 ° C and 21 cm / min using a single spreader bar. (Melt viscosity of 30 Ns / m ² ) reasonably wet drawn product was obtained. At lower temperatures, the samples were poorly wet when the viscosity was high.

Example 6 Wetting of rovings was clearly affected by the number of spreader bars, and under the same working conditions, increasing the number of spreaders achieved an increase in linear velocity for any degree of wetting. it can. The glass fiber used in Example 3 was pultruded at 280 ° C. using PET homopolymer using a single spreader and a speed of 20 cm / min to give a completely wet product (clear). The residence time in the bath under these conditions was about 30 seconds. With three spreaders, the linear velocity could be increased to 120 cm / min and a clear, well-wet pultrusion could be obtained.
The residence time under these conditions was about 10 seconds.

Example 7 Several polymers were used according to the general procedure of Example 1 to make pultruded parts from glass rovings containing 16000 filaments. Pass roving through molten polymer over one spreader bar 15
Subtraction at a rate of cm / min gave in each case a product containing about 65% by weight of glass. The polymers used, the melting temperatures used, the melt viscosities at those temperatures and the properties obtained are detailed in Table 4 below.

[0062]

[Table 4]

In the case of polyethylene terephthalate, the pulling speed was increased above about 15 cm / min and the effect of void content on physical properties was investigated. Table 5 below records the measured properties of the 3 mm diameter rods produced. As these data show, a void content of less than about 5% gives excellent properties.

[0064]

[Table 5]

Example 8 A sample of carbon fiber reinforced polyetherketone was
A carbon fiber tape containing 000 individual filaments was passed through a bath of molten polyetherketone to 40
It was prepared by drawing at a temperature of 0 ° C. and a speed of 25 cm / min. Flexural modulus of 80 GN / m ² , 1200 MN / m
The product was obtained having a ^second breaking stress and 70 mN / m ² of interlaminar shear stress.

Example 9 This example is to demonstrate how the mechanical properties of pultruded moldings vary with fiber volume fraction and resin type. The samples were compared at a fixed volume concentration. The low flexural strength of polypropylene-based composites reflects the tendency of the less rigid resin to fracture in the compression mode. Polypropylene resin is about 1 GN / m
Has a ^second modulus (modulus of elasticity), polyethylene terephthalate has a modulus of about 2GN / m ^2. Pultruded articles were prepared according to the general procedure of Example 1 with a preferred viscosity level of about 3 Ns / m ² of resin.

[0067]

[Table 6]

As this example shows, high modulus resins are clearly superior for applications requiring high compressive strength. Example 10 A sample of 64 wt% glass in PET was pultruded to
A tape having a width of 6 mm and a thickness of 1.4 mm was prepared. The tape was remelted, wound under tension on a 45 mm diameter former, solidified on the former and then allowed to cool. After cooling, the former was pulled out to obtain a tube of wound filament.
Tubes of varying thickness up to 4 mm were wound and formed in this manner.

Example 11 A 3 mm diameter uniaxially oriented pultruded sample based on PET containing 64% by weight glass was remelted and twisted into a helical shape. These twisted rods were bend tested and the stiffness breaking force and total work to failure measured. The total work of failure was determined as the area under the force-deformation curve to failure and, for convenience, is expressed here as a function of the area under the untwisted control sample.

[0070]

[Table 7]

As can be seen from the above results, 11 °
At, there is only a 10% reduction in stiffness and breaking force, while the total work to failure is increased by 30%, improving the balance of properties. At 23 ° both stiffness and strength are reduced by about 60% and the work of failure is 6
It only increases by 0%. Therefore, the optimum twisting is 1
It is shown to be about 1 °.

A pultruded article of a thermoplastic material is more suitable than a thermoset pultruded article because it allows the post-molding to be carried out easily and thus offers the advantage of this energy absorbing mechanism. Example 12 3 mm diameter containing 50% by volume of glass fibers in PET
Pultruded melts were melted at 280 ° C and then braided together. The braided product was less stiff than the uniaxially aligned material, but absorbed more energy in the impact failure test.

Example 13 A flat tape approximately 1.4 mm thick and 6 mm wide formed from a material containing 50% by volume (64% by weight) glass fiber in PET was released into an open tabby weave. Weaved together. Stacking 4 layers of the resulting fabric together, 28
A sheet having a thickness of 3 mm was manufactured by compression molding at 0 ° C. This sheet had the following properties: * Slightly lower values would be expected at an angle of 45 ° to the natural orientation of the fabric.

Example 14 Samples of various pultruded moldings were placed in conventional injection molding molds and compatible polymers were molded around them. The moldings had increased stiffness and strength. Thermoplastic pultruded moldings are particularly suitable for the purpose of strengthening the moldings in this way, since they can be produced with polymers which are completely compatible with the polymer to be molded around the reinforcement.

Example 15 A conventionally compounded material containing 65% by weight glass fiber in PET, chopped to a length of 1 cm, and containing 30% by weight short glass fiber in PET. And then 50/5
Diluted on a 0 basis. The mixture was injection molded using standard techniques to make ASTM bars and properties were compared to a conventionally compounded material containing 50% by weight glass fiber in PET.

[0076]

[Table 8]

Inspection of the ashed portion of the moldings revealed that the majority of long fibers were retained throughout the molding operation. It is believed that this unexpected property results from the low void content in the shredded pultrusion material or the high degree of wetting of the fibers by the polymer. Example 16 Various pultruded samples containing 60% by weight glass fiber containing PET and 60% by weight carbon fiber containing PEEK were cut into 1 cm lengths and described in British Patent Application No. 8101822. Molded according to the method described above. In the method of this UK application, the expanded reinforcing material is produced by extrusion through a short length, preferably zero length die, followed by compression molding to give a three dimensional product containing 60% by weight of long fibers. A molded product was produced.

The pultruded material is particularly suitable for this application because the resulting high level of wetting effectively protects the fibers and reduces interfiber wear that results in fiber breakage. Example 17 Following the procedure of Example 1, using PET having a melt viscosity of 3 Ns / m ² at 280 ° C., approximately 1.4 mm thick × 6 mm wide.
A tape formed at a linear velocity of about 0.2 m / min with a cooled sizing die of.

Not all commercial glass fibers are ideal for pultrusion using thermoplastics.
The most important difference lies in the size system used. Several commercially available grades were compared, along with a study of the effect of crystallinity. At the time of production, the pultruded product was amorphous, but it was easily crystallized by heating to 150 ° C. In Table 9 below, all samples using different glasses are compared at the same weight fraction of 64% by weight glass fiber.

[0080]

[Table 9]

A crystalline morphology that provides high stiffness is preferred in many applications, but the shear stress between layers (ILSS)
It is important to keep high values of, preferably higher than 20 MN / m ² . Example 18 High performance composite materials are often needed to enable use at high temperatures. Using a material containing 64% by weight of glass E used in Example 17 in PET, the properties as set forth in the following table were measured at elevated temperatures for crystalline pultrusion materials.

[0082]

[Table 10]

Example 19 Hot water is a common aggressive environment where the composite material is required to retain its properties. A sample based on 64% by weight of the glass fiber E used in Example 17 was pultruded with PET and immersed in a 95 ° C water bath for various times. The samples were tested both amorphous and crystalline. Properties deteriorated over time, and interlaminar shear strength (ILSS) was the most sensitive property.

[0084]

[Table 11]

In some other glass systems, interlaminar shear strength deteriorated to less than 10 MN / m ² after 4 hours of exposure. Example 20 Fatigue resistance is an important factor in the use properties of composite materials. A sample of a well-moistened pultruded article was prepared based on a material containing 64% by weight of the glass fiber E used in Example 17 in PET. The samples were subjected to a bending test to study the stress / strain relationship at 23 °.
The results obtained are given in the table below.

[0086]

[Table 12]

The sample had a linear elastic limit at 1% strain. The sample was bent at a rate of 1 cycle / 2 seconds using a 70 mm span in a 3-point bend. The number of cycles was recorded for significant damage to be induced (as judged by whitening of the pultrusion). The results obtained are given in the table below.

[0088]

[Table 13]

The samples were strained at 0.1% strain and the properties of the samples were evaluated after different histories. The results obtained are given in the table below.

[0090]

[Table 14]

These tests also included evaluating samples with surfaces that were under tension during the fatigue history in both compression and tension. No difference was observed in these two modes. The properties of the pultrusions were not affected by this fatigue history. Example 21 A tape sample with a thickness of approximately 1.4 mm x a width of 6 mm was prepared using PE.
The material containing the glass fiber used in Example 17 in T was prepared as the main component. The glass content was changed. In all cases, the pultrusions were transparent.

[0092]

[Table 15]

Example 22 High linear velocities are highly desirable for economical production. P
6 of glass fiber D used in Example 17 during ET
A pultrudate containing 9% by weight was formed by drawing the pultrusion through a molten bath containing 5 spreader bars. Wet pultrusions were obtained at the following rates and their properties were measured in bending.

[0094]

[Table 16]

Example 23 A pultrusion was made from the material containing glass fibers E used in Example 17 in PET at 280 ° C. using a single spreader. The viscosity of the resin was changed.
With the resin of very low viscosity, some resin was squeezed from the pultrusion during the molding stage, where the pultrusion was compressed to a width of 6 mm x a thickness of 1.4 mm. Linear velocity 0.2
It was fixed at m / min. The pultruded parts were bend tested in both amorphous and crystalline forms. The crystalline morphology was obtained by heating the sample to 150 ° C. for a short time.

[0096]

[Table 17]

As is evident from the above results, the very low viscosity samples provided useful properties in the amorphous state, but upon crystallization the properties deteriorated. At high viscosities, the glass was poorly wet (and thus gave a low resin concentration). Example 24 The tape of glass fiber E used in Example 17 is
By pultrusion on a single spreader (in PET with a melt viscosity of 3 Ns / m ² at 280 ° C.) and mixing well wetted, 6 mm wide, but different amounts of glass, Tapes of varying thickness were obtained. The sample tested was amorphous.

[0098]

[Table 18]

Example 25 Glass fibers having different diameters were pultruded with PET. The samples tested in amorphous had the following properties.

[0100]

[Table 19]

Example 26 The glass fiber E used in Example 17 is treated with polyethersulfone having a melt viscosity of 8 Ns / m ² at 350 ° C. in a single spreader system at 0.2 m / min. Impregnation was performed at a linear velocity of. The following properties were obtained.

[0102]

[Table 20]

Example 27 Carbon fiber was impregnated at 0.2 m / min in a single spreader pultrusion apparatus using PEEK having a melt viscosity of 30 Ns / m ² at 380 ° C. A rod with a diameter of 3 mm containing 60% by weight of carbon fibers was formed. Example 28 Conventional glass-filled PET (intrinsic viscosity 0.7
A blend was prepared from short fiber compound made by extrusion compounding with 5 of PET) and chopped into 10 mm pultruded parts (manufactured according to Example 3).
Injection molding of these blends, thickness 1.5mm x width 1
Filling from 0mm rectangular side gate, diameter 114
A disc having a thickness of 3 mm and a thickness of 3 mm was formed. These samples were exposed to impact in an instrumented drop weight impact test and the failure energy recorded.

[0104]

[Table 21]

All samples were filled into molds with similar ease. Because the polymer used to make the pultrusion was of lower molecular weight than the polymer used to make the short fiber blend, and this low molecular weight polymer offset the increased flow resistance due to long fibers Because. The results clearly show an increase in the failure energy of the long fiber filler material despite the low molecular weight of the polymer, which is usually expected to contribute to brittleness. Especially, the test No.
2 and No. 4 and the same total weight% of fibers should be compared.

Further, the molded product of the short fibers is torn when an impact is applied to cause a sharp plastic piece to fly off.
It was observed that when more than half of the weight fraction was long fibers, the moldings broke in a safe manner and all the broken pieces remained bonded to the main part. Ashing the molding after testing revealed that many of the long glass fibers retained most of their original length. Significantly more than 50% by weight of the original length of fibers in the molding was greater than 3 mm.

The samples were also evaluated for flexural modulus, anisotropy ratio, Izod impact strength, and intrinsic viscosity (IV) of the polymer in the molding. The values in Table 22 below indicate reduced anisotropy and good notched impact strength for short fiber products.

[0108]

[Table 22]

Example 29 Fourteen tapes of continuous carbon fiber (carbon fiber supplied by Courtland, labeled XAS), each containing 6000 individual filaments, were drawn at a speed of 25 cm / min. The stationary guide bar of the series was pulled over to form a band about 50 mm wide having a tension of about 100 pounds (45.4 kg). When the fibers were guided into an abutting relationship, they were pulled on a single fixed heated cylindrical bar of diameter 12.5 mm. The temperature of the bar was maintained at about 380 ° C. A powder of polyetheretherketone having a melt viscosity of ²⁰ Ns / m ² at this temperature was fed into the nip formed between the band of carbon fibers and the fixed roller. The powder melted rapidly forming a pool of melt in the nip, which melt impregnated a band of fibers passing over a roller. The construction was passed over and under five additional heated bars without adding additional amounts of polymer. It contains 58% by volume of carbon fibers and has a thickness of 0.
A carbon fiber reinforced sheet of 125 mm was produced. The product was found to have the following properties.

Flexural Modulus 130 GN / m ² Flexural Strength 1400 MN / m ² Interlaminar Shear Strength 90 MN / m ² Example 30 The procedure of Example 29 was followed. In this example, 360 ° C
A polyether sulfone having a melt viscosity of 3 Ns / m ² in was used to produce a reinforced product containing 40% by volume of carbon fiber. Roller temperature is about 36
Maintained at 0 ° C. The product had a flexural modulus and flexural strength of 700MN / m ² of 80GN / m ^2.

Example 31 The procedure of Example 29 was followed. In this example, 360 ° C
In Commercial having a viscosity of 800 ns / m ² to available polyethersulfone PES 200P (Imperial
Available from Chemikacal Industries PLS)
It was used. The roller temperature was maintained at about 360 ° C. A product containing 44% by volume of carbon fiber was produced. The product had the following properties.

Flexural Modulus 60 GN / m ² Flexural Strength 500 MN / m ² Interlaminar Shear Strength 25 MN / m ² Example 32 The general procedure of Example 29 was followed. In this example, an impregnated sheet was made using 14 tapes of continuous carbon fiber ("Coultaulds" XAS, 6K tow) and polyetheretherketone having a melt viscosity of 30 Ns / m ² at 370 ° C. In the device, each diameter is 12.
Five cylindrical bars of 5 mm were heated to 380 ° C. 1
The four tapes were pulled under tension to form a band 50mm wide, which was passed through the adjustable nip formed by the first two bars with the ordinate horizontal. This band was subsequently passed under and over three additional heated bars with the vertical axis also horizontal. The first two bars were used to form a nip so that the polymer could be fed to both sides of the band. To prevent polymer spillage, two retaining metal sheets were placed in contact with and along the length of the two heated bars to form a feed trough. Polymer powder was fed to both sides of the band passing through the first two heated bars. The powder melted rapidly forming a pool of melt in two nips formed between the sides of the band and each heating bar. Adjusting the gap between the first two bars, the carbon fiber was coated with polymer when the pulling speed was 0.5 m / min, and the resulting impregnated tape contained about 60% by weight of carbon fiber. It contained 40% by weight of polymer. It has been found that adjusting the fiber content can be achieved in several ways.

1. 1. Change the nip gap, 2. changing the pre-tension, 3. Change the number of filaments supplied to the nip, 4. changing the feed rate of the powder, Changing the temperature of the bar in the nip (for the resin used in this example the preferred temperature range was below 400 ° C. for decomposition and above 360 ° C. for the onset of crystallization), 6. Change the pulling speed. The tape thus formed appeared well-wetted and was about 0.1 mm thick.

Example 33 The tape described in Example 32 was cut to a length of 150 mm and stacked in a matched die compression molding machine. The molding machine was heated to 380 ° C. in a conventional laboratory press and compressed so that the moldings received a pressure of 2-5 × 10 ⁶ N / m ² . The molding was held at that pressure for 10 minutes (it took half the time for the mold and sample to reach equilibrium temperature) and then cooled to 150 ° C. under pressure before being removed from the press. The cooling step took approximately 20 minutes. The mold was cooled to ambient temperature and the molding was removed.

Moldings having a thickness in the range of 0.5 mm (4 plies) to 4 mm (38 plies) were formed as described above. During the molding operation, a small amount of polymer was squeezed out of the mold as a flash so that the molding contained 62% by weight of carbon fibers compared to 60% by weight in the original tape.
The moldings were then sawed with a diamond wafer saw to form a sample suitable for mechanical testing by the bending technique. The following results were obtained.

[0116] specimen of electrolyte span / depth ratio value flexural modulus 70: 1 130 GN / m ² Flexural modulus 30: 1 115 (6) GN / m 2 Flexural strength 30: 1 1191 (55) MN / M ² Bending strength in lateral direction 5: 1 98 (11) MN / m ² Shear strength between layers 5: 1 81 (4) MN / m ² (Numbers in parentheses indicate standard deviation) Example 34 Using the same equipment as in Example 32, some less wettable tapes were made by using less feed in some parts of the tape and more feed in other parts.
The total fiber content of the tape was the same as in Example 4, but much of the released fiber appeared on the surface of the tape and other areas were resin rich.

The tapes were stacked and molded as described in Example 33, taking care that the less wetted areas of one tape were located adjacent to the resin-rich area of the next tape. . Visual inspection of the molding left a substantially non-wettable area and the released fibers could be easily pulled from the surface. The mechanical properties of these moldings were inferior to those found in Example 33, and in particular the interlaminar shear strength varied and 10 MN
Low values of / m ² (compared to 81 for well-wetted samples) were common.

As this example shows, wetting of the fibers occurs predominantly during the impregnation stage and not during the secondary molding stage. However, it is believed that higher pressures and longer residence times could achieve some wetting. Example 35 The tape prepared in Example 29 was torn to give a thickness of about 15 mm.
Width tapes, and these tapes in tabby weave (as described in the Encyclopedia Bricanica Textiles section)
Was woven into a sheet approximately 150 mm square.

Example 36 The single woven sheet described in Example 35 is used in Example 33.
Was compression molded as described in Example 1 except that the molding was simply performed between aluminum sheets with the sidewalls unconstrained.
The molding was a flat sheet with a thickness of 0.2 mm. In an additional experiment, five woven sheets as described in Example 7 were layered together so that each layer was oriented ± 45 ° with respect to the layers above and below it. This laminate was compression-molded without constraining the side wall to form a sheet having a thickness of 1 mm. A 135 mm diameter disc was cut from this sheet and the stiffness and strength of the disc was measured by C.I. J. Hooley and S.H. Technology described by Turner (Mechanica)
l Testing of Plastics, Inst
itute of Mechanical Engineering
eers, June / Jully 1979, Autom
It was measured using a disk bending test and an automated falling weight impact test according to the Active Engineer).

[0120] bending stiffness of the plate had a maximum value and the minimum value of the 36GN / m ² of 50GN / m ^2. The impact resistance of the sheet was as follows: initial energy 1.7 (0.3) J failure energy 6.6 (1.1) J (standard deviation in parentheses) line of maximum stiffness. A sample with parallel sides cut along it was measured in a normal bending test with the following results.

Flexural Modulus 51 GN / m ² Flexural Strength 700 GN / m ² Example 37 Disks with a diameter of 135 mm and a thickness of 1 mm were prepared according to the procedure of Example 36, and 3 J of 3 J distributed evenly over the surface of this disk. It was subjected to 19 shocks. These impacts caused some delamination, but the damaged moldings remained cohesive.

The damaged disc was then reshaped and then tested as described in Example 36. The following results were obtained. Damaged and reformed Original shape (Example 5) Bending rigidity (maximum) 51GN / m ² 50GN / m ² Bending rigidity (minimum) 37GN / m ² 36GN / m ² Impact initial 1.9 (0 .1) J 1.7 (0.3) J Impact damage 6.5 (2.8) J 6.6 (1.1) J (standard deviation in parentheses) As can be easily understood, There is no significant difference in the above results.

As this example shows, after partial damage,
Nature fully regenerates. Example 38 A damaged disk prepared as in Example 37 was ruptured with 5 impacts using the instrument drop weight impact test.
The damage was localized to a region that was not much larger than the cross section of the impactor, and all the fractured parts remained bonded to the body of the molding.

Then, the destroyed molded product is remolded,
The impact test was then carried out, taking care to direct the new impact to the previously destroyed spot. The following results were obtained. Initial energy 1.8 (0.4) J Failure energy 4.6 (0.8) J (standard deviation in parentheses) By comparing with the results of Examples 33 and 34, the above results show that It shows that in bad cases, almost 70% of the original strength can be recorded.

Example 39 Diameter 135 mm made according to Example 36, thickness approximately 1
mm disc heated to 380 ° C, then 200 mm in diameter
Was placed in half of the normal temperature hemispherical female mold. Half of the male mold of this mold was pressed down by hand to form a hemispherical part having a radius of curvature of 100 mm. Portions up to about 100 mm in diameter (with a solid angle of about 60 ° from the center of the sphere forming a part) fit the double curvature well, but some waviness occurred outside this region.

Example 40 A woven sheet was prepared from 5 mm wide tape using 5 satin weaves (described in the Britannica Encyclopedia Textiles section). In the dry state, this fabric gave a doubly curved surface a very good composition and did not form pores in the fabric. Manufactures a five-layer quasi-isotropic sheet,
It was then molded as described in Example 36. This 1mm
Sheets of the following thickness were then heated to 380 ° C. and molded against various cold surfaces including: Right angle, cylindrical surface with radius of curvature 2.25 mm, spherical surface with radius of curvature 3.15 mm.

Good agreement was obtained in cases 1 and 2 above. For double curvature, stretch from the center of the sphere 6
Good agreement was obtained up to a solid angle of 0 ° (which is similar to the experiment of Example 39, but at a tighter radius of curvature with respect to the thickness of the sheet). The largest structures require only a gentle double curvature, but a tight weave requires a narrow weave, which is preferred over wide tabby weaves, especially in satin weaves, according to the general experience of the textile industry.

Example 41 One 40 mm square material was woven from a tape having a width of 2 mm and a thickness of 0.1 mm (tabby weave). The formability of a sheet of this material was compared to that of the wide tape fabric described in Example 35. The narrow tape could easily adapt to shape changes.
Molded sheets formed from these two fabrics appeared superficially similar in nature.

It is believed that narrow tapes may actually be used for the purpose of using conventional textile techniques. Example 42 The tapes formed in Example 32 were stacked to try to form a multilayer composite with each layer having a different orientation.
Since the tape was not "sticky" at room temperature when freshly formed, the layers tended to move with respect to each other during the placement and molding operations, so the fibers did not orient in the designed configuration in the final molding. It was This problem was partially overcome by locally tacking the layers together with a soldering iron. When molded in this manner, the sheet had to be molded by constraining the sidewalls to prevent the fibers from flowing laterally and disturbing the pattern of the designed orientation.

In contrast, woven sheets are convenient and easy to handle, and the interlocking tissue itself prevents lateral movement of the fibers, so molding is performed without constraining the sidewalls. I was able to. The ability to form a preferred sheet without constraining the sidewalls is particularly advantageous when considering the production of continuous sheets by methods such as double band pressing.

Example 43 The woven sheets of Example 35 were stacked and molded to form sheets of different thickness, each layer being at ± 45 ° with respect to the layers above and below it. The impact behavior of these sheets was determined by an instrumentation drop weight impact test. The results obtained are given in the table below.

[0132]

[Table 23]

Example 44 Polyethersulfone "Vi" was prepared according to the procedure of Example 32.
ctrex "200P and carbon fiber (Courtau
lds XAS, N.I. Size) to tape.
This polymer has 800 Ns / m ² at 350 ° C., and 40
It had a melt viscosity of 100 Ns / m ² at 0 ° C. The spreader was controlled at about 370-380 ° C and the pulling speed was 0.2 m / min. The tape did not wet as well as described in Example 32 due to the high viscosity of this resin. The resin content was increased slightly so that the final tape contained 50 wt% carbon fiber and 50 wt% resin.

A sample was formed as described in Example 33 to form a uniaxially oriented sheet having the following properties: Flexural modulus 60 GN / m ² Flexural strength 500 MN / m ² Transverse bending Strength 20 MN / m ² Interlaminar Shear Strength 26 MN / m ² The tape was then woven according to Examples 35 and 36,
The sheets were laminated and molded to form a sheet having a thickness of approximately 1 mm and having the following properties: Bending rigidity (maximum) 24 GN / m ² Bending rigidity (minimum) 21 GN / m ² Impact energy (initial) 2 .9 (0.3) J Impact Energy (Failure) 7.1 (0.3) J (standard deviation in parentheses) Reformed broken sheet and sample at same spot as original impact damage Be careful not to shock
Retested.

The flexural rigidity of the reformed sheet was 10% lower than that of the original sheet, but the impact resistance was reduced to 60% of its original value. Example 45 Polyethersulfone having a melt viscosity of 8 Ns / m ² at 350 ° C. was used to impregnate a tape of carbon fibers. The carbon fibers were previously sized with 5% by weight of polyethersulfone by the solution sizing method.
This sample was impregnated by pulling it over four spreaders heated to 350 ° C. at a speed of 0.2 m / min. The final composite material contained 47% by weight carbon fibers. A sample was molded and tested according to Example 30 with the following results: flexural modulus 85 GN / m ² flexural strength 680 MN / m ² interlaminar shear strength 50 MN / m ² This sample was run. Although made from a lower molecular weight polymer than that used in Example 44, it is noted that the composite has excellent properties.

Example 46 A glass roving made of polyethylene terephthalate (2
Impregnation was carried out at 70 ° C. with a melt viscosity of 3 Ns / m ² ) according to the procedure described in Example 32, but using a 280-300 ° C. bar. Up to 80% by weight of glass fibers were satisfactorily incorporated to give excellent wetting. At 60% by weight glass, a linear velocity of 5 m / min was easily achieved for a tape with a thickness of 0.1 mm.

Example 47 A glass roving was impregnated with polypropylene having a melt viscosity of 10 Ns / m ² at 270 ° C., using the same equipment as in Example 32, but maintaining the bar at 270 ° C. Very wet 0.1 mm at 50% by weight of glass fiber
Thickness of tape was obtained, which was especially useful for overlapping tubes and other parts made from polypropylene.

Example 48 Contains residues of hydroxynaphthoic acid, terephthalic acid and hydroquinone and has a melt viscosity at 320 ° C. of 7 Ns /
m ² is a thermochromic polyester, carbon fiber (“Ce
lion "6K and 3K tow). The equipment was identical to that described in Example 32, except that the bar was maintained at 320 ° C. 0.1 mm containing 62% by weight carbon fiber. The thick tape had an excellent appearance.

Example 49 Examples 32-38, including certain materials with excess resin.
Various pieces of scrap material produced from B.S.A. were broken and fed to a conventional screw extruder and compounded to form granules. The granules contained carbon fibers with a thickness of up to 0.25 mm. These granules, according to the usual molding technique,
Injection molded under standard operating conditions for filled PEEK. The molded product had the properties as shown in the following table. In addition, these properties, manufactured by ordinary compounding work,
Compare to the properties of the best available commercial grade carbon fiber filled PEEK: Scrap formulation Weight% of best commercial grade carbon fiber 55 30 Modulus 32 GN / m ² 13 GN / m ² Tensile strength 250 MN / m ² 190 MN / m ² surface quality excellent excellent As is apparent from this example, the product of the invention can be converted into a product for common processing methods, which product can be obtained by the state of the art. Better in some ways than things. Also, scrap from various long fiber operations, such as sheet production, lamination, and filament winding, can be reclaimed into high performance materials. The renewable nature has great economic implications when working with expensive raw materials such as carbon fiber.

Example 50 The optimum tension during roving when operating according to the method of Example 29 is determined by measuring the tension in individual rovings containing 6000 filaments before impregnation and in the tensioning stage. Did (14
Book roving was used in Example 29, and the working tension will actually be 14 times the value below). The values below were determined to be the minimum working tension (case 1) and the maximum working tension (case 2) for the particular roving, polymer type and equipment used. Using tension values less than those of Case 1, there were fiber misalignments and tears in the tapes produced. With tension values higher than those in Case 2, fiber wear was observed and released fibers accumulated on the band. Although different values were obtained for different sets of conditions (roving, polymer type, etc.), they could be easily optimized to give excellent quality products.

Tension before impregnation Tensile tension Case 1 0.14 kg 2.4 kg Case 2 0.37 kg 3.8 kg

[0142]

As is apparent from the above description, according to the present invention, in the fiber reinforced pellet structure, (a) the fiber content can be increased, (b) the degree of wetting of individual filaments wetted by the impregnated polymer C) When a pellet structure is used as a molded product, the appearance of the molded product obtained is good. D) When a pellet structure is used as a molded product, there is a loss in filament length. You can obtain effects such as never.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number 8134597 (32) Priority date November 17, 1981 (33) Priority claim country United Kingdom (GB) (31) Priority claim number 8134598 (32) Priority date November 17, 1981 (33) Priority countries United Kingdom (GB) (72) Inventor Frederick Neil Cogswell United Kingdom, Hertz AE 71 1H Day, Welwyn Garden City, Bethemer Road, Pea Box No. 6 (72) Inventor David John Hezel United Kingdom, Hertz Ahl 71 1st Day, Welwyn Garden City, Bethemer Road, Peaux Box No. 6 (72) Inventor Peter John Williams United Kingdom, Ha Tsu vinylethers 7 1 EI Chide, Welwyn Garden Citi, Besema load, peak O box number 6

Claims (1)

[Claims] 1. A pellet structure having a length of 3 to 100 mm and comprising a thermoplastic resin and at least 30% by volume of parallel aligned reinforcing filaments, said pellet structure comprising: Void content defined by the following formula (I): Of less than 15% has the form of pellets chopped into a continuous structure, and the individual filaments contained in the pellet structure are substantially separated by the thermoplastic resin in a melt pultrusion process. That the pellet structure is injection molded,
A molded article in which the filaments in the molded article obtained after molding have the form of randomly dispersed individual filaments and at least 50% by weight of the filaments have a length of at least 3 mm. A fiber-reinforced pellet structure for thermoforming, characterized by being moldable.